diff --git a/src/TestFramework/TestFramework/Assertions/Assert.AreEqual.cs b/src/TestFramework/TestFramework/Assertions/Assert.AreEqual.cs
index 247607a66b..15d3882f73 100644
--- a/src/TestFramework/TestFramework/Assertions/Assert.AreEqual.cs
+++ b/src/TestFramework/TestFramework/Assertions/Assert.AreEqual.cs
@@ -1277,7 +1277,7 @@ public static void AreEqual(string? expected, string? actual, bool ignoreCase,
 #pragma warning restore IDE0060 // Remove unused parameter
         CultureInfo culture, [InterpolatedStringHandlerArgument(nameof(expected), nameof(actual), nameof(ignoreCase), nameof(culture))] ref AssertNonGenericAreEqualInterpolatedStringHandler message, [CallerArgumentExpression(nameof(expected))] string expectedExpression = "", [CallerArgumentExpression(nameof(actual))] string actualExpression = "")
     {
-        CheckParameterNotNull(culture, "Assert.AreEqual", nameof(culture), string.Empty);
+        CheckParameterNotNull(culture, "Assert.AreEqual", nameof(culture));
         message.ComputeAssertion(expectedExpression, actualExpression);
     }
 
@@ -1316,7 +1316,7 @@ public static void AreEqual(string? expected, string? actual, bool ignoreCase,
     /// </exception>
     public static void AreEqual(string? expected, string? actual, bool ignoreCase, CultureInfo culture, string? message = "", [CallerArgumentExpression(nameof(expected))] string expectedExpression = "", [CallerArgumentExpression(nameof(actual))] string actualExpression = "")
     {
-        CheckParameterNotNull(culture, "Assert.AreEqual", "culture", string.Empty);
+        CheckParameterNotNull(culture, "Assert.AreEqual", "culture");
         if (!AreEqualFailing(expected, actual, ignoreCase, culture))
         {
             return;
@@ -1372,7 +1372,7 @@ public static void AreNotEqual(string? notExpected, string? actual, bool ignoreC
 #pragma warning restore IDE0060 // Remove unused parameter
         CultureInfo culture, [InterpolatedStringHandlerArgument(nameof(notExpected), nameof(actual), nameof(ignoreCase), nameof(culture))] ref AssertNonGenericAreNotEqualInterpolatedStringHandler message, [CallerArgumentExpression(nameof(notExpected))] string notExpectedExpression = "", [CallerArgumentExpression(nameof(actual))] string actualExpression = "")
     {
-        CheckParameterNotNull(culture, "Assert.AreNotEqual", nameof(culture), string.Empty);
+        CheckParameterNotNull(culture, "Assert.AreNotEqual", nameof(culture));
         message.ComputeAssertion(notExpectedExpression, actualExpression);
     }
 
@@ -1412,7 +1412,7 @@ public static void AreNotEqual(string? notExpected, string? actual, bool ignoreC
     /// </exception>
     public static void AreNotEqual(string? notExpected, string? actual, bool ignoreCase, CultureInfo culture, string? message = "", [CallerArgumentExpression(nameof(notExpected))] string notExpectedExpression = "", [CallerArgumentExpression(nameof(actual))] string actualExpression = "")
     {
-        CheckParameterNotNull(culture, "Assert.AreNotEqual", "culture", string.Empty);
+        CheckParameterNotNull(culture, "Assert.AreNotEqual", "culture");
         if (!AreNotEqualFailing(notExpected, actual, ignoreCase, culture))
         {
             return;
diff --git a/src/TestFramework/TestFramework/Assertions/Assert.Contains.cs b/src/TestFramework/TestFramework/Assertions/Assert.Contains.cs
index 0a70e0747f..05f36ec2a4 100644
--- a/src/TestFramework/TestFramework/Assertions/Assert.Contains.cs
+++ b/src/TestFramework/TestFramework/Assertions/Assert.Contains.cs
@@ -133,7 +133,7 @@ public static T ContainsSingle<T>(IEnumerable<T> collection, string? message = "
     /// Users shouldn't pass a value for this parameter.
     /// </param>
     /// <returns>The item.</returns>
-    public static object ContainsSingle(IEnumerable collection, string? message = "", [CallerArgumentExpression(nameof(collection))] string collectionExpression = "")
+    public static object? ContainsSingle(IEnumerable collection, string? message = "", [CallerArgumentExpression(nameof(collection))] string collectionExpression = "")
         => ContainsSingle(static _ => true, collection, message, predicateExpression: string.Empty, collectionExpression);
 
     /// <summary>
@@ -192,33 +192,35 @@ public static T ContainsSingle<T>(Func<T, bool> predicate, IEnumerable<T> collec
     /// Users shouldn't pass a value for this parameter.
     /// </param>
     /// <returns>The item that matches the predicate.</returns>
-    public static object ContainsSingle(Func<object, bool> predicate, IEnumerable collection, string? message = "", [CallerArgumentExpression(nameof(predicate))] string predicateExpression = "", [CallerArgumentExpression(nameof(collection))] string collectionExpression = "")
+    public static object? ContainsSingle(Func<object, bool> predicate, IEnumerable collection, string? message = "", [CallerArgumentExpression(nameof(predicate))] string predicateExpression = "", [CallerArgumentExpression(nameof(collection))] string collectionExpression = "")
     {
         object? firstMatch = null;
         int matchCount = 0;
 
         foreach (object? item in collection)
         {
-            if (predicate(item))
+            if (!predicate(item))
             {
-                if (matchCount == 0)
-                {
-                    firstMatch = item;
-                }
-
-                matchCount++;
-
-                // Early exit optimization - no need to continue if we already have more than one match
-                if (matchCount > 1)
-                {
-                    break;
-                }
+                continue;
+            }
+
+            if (matchCount == 0)
+            {
+                firstMatch = item;
+            }
+
+            matchCount++;
+
+            // Early exit optimization - no need to continue if we already have more than one match
+            if (matchCount > 1)
+            {
+                break;
             }
         }
 
         if (matchCount == 1)
         {
-            return firstMatch!;
+            return firstMatch;
         }
 
         if (string.IsNullOrEmpty(predicateExpression))
@@ -232,7 +234,7 @@ public static object ContainsSingle(Func<object, bool> predicate, IEnumerable co
             ThrowAssertSingleMatchFailed(matchCount, userMessage);
         }
 
-        return default!;
+        return default;
     }
 
     #endregion // ContainsSingle
@@ -279,6 +281,8 @@ public static void Contains<T>(T expected, IEnumerable<T> collection, string? me
     /// </param>
     public static void Contains(object? expected, IEnumerable collection, string? message = "", [CallerArgumentExpression(nameof(expected))] string expectedExpression = "", [CallerArgumentExpression(nameof(collection))] string collectionExpression = "")
     {
+        CheckParameterNotNull(collection, "Assert.Contains", "collection");
+
         foreach (object? item in collection)
         {
             if (object.Equals(item, expected))
@@ -333,6 +337,9 @@ public static void Contains<T>(T expected, IEnumerable<T> collection, IEqualityC
     /// </param>
     public static void Contains(object? expected, IEnumerable collection, IEqualityComparer comparer, string? message = "", [CallerArgumentExpression(nameof(expected))] string expectedExpression = "", [CallerArgumentExpression(nameof(collection))] string collectionExpression = "")
     {
+        CheckParameterNotNull(collection, "Assert.Contains", "collection");
+        CheckParameterNotNull(comparer, "Assert.Contains", "comparer");
+
         foreach (object? item in collection)
         {
             if (comparer.Equals(item, expected))
@@ -385,6 +392,9 @@ public static void Contains<T>(Func<T, bool> predicate, IEnumerable<T> collectio
     /// </param>
     public static void Contains(Func<object?, bool> predicate, IEnumerable collection, string? message = "", [CallerArgumentExpression(nameof(predicate))] string predicateExpression = "", [CallerArgumentExpression(nameof(collection))] string collectionExpression = "")
     {
+        CheckParameterNotNull(collection, "Assert.Contains", "collection");
+        CheckParameterNotNull(predicate, "Assert.Contains", "predicate");
+
         foreach (object? item in collection)
         {
             if (predicate(item))
@@ -461,6 +471,9 @@ public static void Contains(string substring, string value, string? message = ""
     /// </exception>
     public static void Contains(string substring, string value, StringComparison comparisonType, string? message = "", [CallerArgumentExpression(nameof(substring))] string substringExpression = "", [CallerArgumentExpression(nameof(value))] string valueExpression = "")
     {
+        CheckParameterNotNull(value, "Assert.Contains", "value");
+        CheckParameterNotNull(substring, "Assert.Contains", "substring");
+
         if (!value.Contains(substring, comparisonType))
         {
             string userMessage = BuildUserMessageForSubstringExpressionAndValueExpression(message, substringExpression, valueExpression);
@@ -513,6 +526,8 @@ public static void DoesNotContain<T>(T notExpected, IEnumerable<T> collection, s
     /// </param>
     public static void DoesNotContain(object? notExpected, IEnumerable collection, string? message = "", [CallerArgumentExpression(nameof(notExpected))] string notExpectedExpression = "", [CallerArgumentExpression(nameof(collection))] string collectionExpression = "")
     {
+        CheckParameterNotNull(collection, "Assert.DoesNotContain", "collection");
+
         foreach (object? item in collection)
         {
             if (object.Equals(notExpected, item))
@@ -565,6 +580,9 @@ public static void DoesNotContain<T>(T notExpected, IEnumerable<T> collection, I
     /// </param>
     public static void DoesNotContain(object? notExpected, IEnumerable collection, IEqualityComparer comparer, string? message = "", [CallerArgumentExpression(nameof(notExpected))] string notExpectedExpression = "", [CallerArgumentExpression(nameof(collection))] string collectionExpression = "")
     {
+        CheckParameterNotNull(collection, "Assert.DoesNotContain", "collection");
+        CheckParameterNotNull(comparer, "Assert.DoesNotContain", "comparer");
+
         foreach (object? item in collection)
         {
             if (comparer.Equals(item, notExpected))
@@ -615,6 +633,9 @@ public static void DoesNotContain<T>(Func<T, bool> predicate, IEnumerable<T> col
     /// </param>
     public static void DoesNotContain(Func<object?, bool> predicate, IEnumerable collection, string? message = "", [CallerArgumentExpression(nameof(predicate))] string predicateExpression = "", [CallerArgumentExpression(nameof(collection))] string collectionExpression = "")
     {
+        CheckParameterNotNull(collection, "Assert.DoesNotContain", "collection");
+        CheckParameterNotNull(predicate, "Assert.DoesNotContain", "predicate");
+
         foreach (object? item in collection)
         {
             if (predicate(item))
@@ -689,6 +710,9 @@ public static void DoesNotContain(string substring, string value, string? messag
     /// </exception>
     public static void DoesNotContain(string substring, string value, StringComparison comparisonType, string? message = "", [CallerArgumentExpression(nameof(substring))] string substringExpression = "", [CallerArgumentExpression(nameof(value))] string valueExpression = "")
     {
+        CheckParameterNotNull(value, "Assert.DoesNotContain", "value");
+        CheckParameterNotNull(substring, "Assert.DoesNotContain", "substring");
+
         if (value.Contains(substring, comparisonType))
         {
             string userMessage = BuildUserMessageForSubstringExpressionAndValueExpression(message, substringExpression, valueExpression);
diff --git a/src/TestFramework/TestFramework/Assertions/Assert.EndsWith.cs b/src/TestFramework/TestFramework/Assertions/Assert.EndsWith.cs
index 8463f8e44a..772c1d1e48 100644
--- a/src/TestFramework/TestFramework/Assertions/Assert.EndsWith.cs
+++ b/src/TestFramework/TestFramework/Assertions/Assert.EndsWith.cs
@@ -72,8 +72,8 @@ public static void EndsWith([NotNull] string? expectedSuffix, [NotNull] string?
     /// </exception>
     public static void EndsWith([NotNull] string? expectedSuffix, [NotNull] string? value, StringComparison comparisonType, string? message = "", [CallerArgumentExpression(nameof(expectedSuffix))] string expectedSuffixExpression = "", [CallerArgumentExpression(nameof(value))] string valueExpression = "")
     {
-        CheckParameterNotNull(value, "Assert.EndsWith", "value", string.Empty);
-        CheckParameterNotNull(expectedSuffix, "Assert.EndsWith", "expectedSuffix", string.Empty);
+        CheckParameterNotNull(value, "Assert.EndsWith", "value");
+        CheckParameterNotNull(expectedSuffix, "Assert.EndsWith", "expectedSuffix");
         if (!value.EndsWith(expectedSuffix, comparisonType))
         {
             string userMessage = BuildUserMessageForExpectedSuffixExpressionAndValueExpression(message, expectedSuffixExpression, valueExpression);
@@ -146,8 +146,8 @@ public static void DoesNotEndWith([NotNull] string? notExpectedSuffix, [NotNull]
     /// </exception>
     public static void DoesNotEndWith([NotNull] string? notExpectedSuffix, [NotNull] string? value, StringComparison comparisonType, string? message = "", [CallerArgumentExpression(nameof(notExpectedSuffix))] string notExpectedSuffixExpression = "", [CallerArgumentExpression(nameof(value))] string valueExpression = "")
     {
-        CheckParameterNotNull(value, "Assert.DoesNotEndWith", "value", string.Empty);
-        CheckParameterNotNull(notExpectedSuffix, "Assert.DoesNotEndWith", "notExpectedSuffix", string.Empty);
+        CheckParameterNotNull(value, "Assert.DoesNotEndWith", "value");
+        CheckParameterNotNull(notExpectedSuffix, "Assert.DoesNotEndWith", "notExpectedSuffix");
         if (value.EndsWith(notExpectedSuffix, comparisonType))
         {
             string userMessage = BuildUserMessageForNotExpectedSuffixExpressionAndValueExpression(message, notExpectedSuffixExpression, valueExpression);
diff --git a/src/TestFramework/TestFramework/Assertions/Assert.Matches.cs b/src/TestFramework/TestFramework/Assertions/Assert.Matches.cs
index fe834bb6ae..b204970b6d 100644
--- a/src/TestFramework/TestFramework/Assertions/Assert.Matches.cs
+++ b/src/TestFramework/TestFramework/Assertions/Assert.Matches.cs
@@ -39,8 +39,8 @@ public sealed partial class Assert
     /// </exception>
     public static void MatchesRegex([NotNull] Regex? pattern, [NotNull] string? value, string? message = "", [CallerArgumentExpression(nameof(pattern))] string patternExpression = "", [CallerArgumentExpression(nameof(value))] string valueExpression = "")
     {
-        CheckParameterNotNull(value, "Assert.MatchesRegex", "value", string.Empty);
-        CheckParameterNotNull(pattern, "Assert.MatchesRegex", "pattern", string.Empty);
+        CheckParameterNotNull(value, "Assert.MatchesRegex", "value");
+        CheckParameterNotNull(pattern, "Assert.MatchesRegex", "pattern");
 
         if (!pattern.IsMatch(value))
         {
@@ -115,8 +115,8 @@ public static void MatchesRegex([NotNull] string? pattern, [NotNull] string? val
     /// </exception>
     public static void DoesNotMatchRegex([NotNull] Regex? pattern, [NotNull] string? value, string? message = "", [CallerArgumentExpression(nameof(pattern))] string patternExpression = "", [CallerArgumentExpression(nameof(value))] string valueExpression = "")
     {
-        CheckParameterNotNull(value, "Assert.DoesNotMatchRegex", "value", string.Empty);
-        CheckParameterNotNull(pattern, "Assert.DoesNotMatchRegex", "pattern", string.Empty);
+        CheckParameterNotNull(value, "Assert.DoesNotMatchRegex", "value");
+        CheckParameterNotNull(pattern, "Assert.DoesNotMatchRegex", "pattern");
 
         if (pattern.IsMatch(value))
         {
@@ -161,7 +161,7 @@ public static void DoesNotMatchRegex([NotNull] string? pattern, [NotNull] string
 
     private static Regex? ToRegex([NotNull] string? pattern)
     {
-        CheckParameterNotNull(pattern, "Assert.MatchesRegex", "pattern", string.Empty);
+        CheckParameterNotNull(pattern, "Assert.MatchesRegex", "pattern");
         return new Regex(pattern);
     }
 }
diff --git a/src/TestFramework/TestFramework/Assertions/Assert.StartsWith.cs b/src/TestFramework/TestFramework/Assertions/Assert.StartsWith.cs
index 7a6fe16fad..6f5c728535 100644
--- a/src/TestFramework/TestFramework/Assertions/Assert.StartsWith.cs
+++ b/src/TestFramework/TestFramework/Assertions/Assert.StartsWith.cs
@@ -72,8 +72,8 @@ public static void StartsWith([NotNull] string? expectedPrefix, [NotNull] string
     /// </exception>
     public static void StartsWith([NotNull] string? expectedPrefix, [NotNull] string? value, StringComparison comparisonType, string? message = "", [CallerArgumentExpression(nameof(expectedPrefix))] string expectedPrefixExpression = "", [CallerArgumentExpression(nameof(value))] string valueExpression = "")
     {
-        CheckParameterNotNull(value, "Assert.StartsWith", "value", string.Empty);
-        CheckParameterNotNull(expectedPrefix, "Assert.StartsWith", "expectedPrefix", string.Empty);
+        CheckParameterNotNull(value, "Assert.StartsWith", "value");
+        CheckParameterNotNull(expectedPrefix, "Assert.StartsWith", "expectedPrefix");
         if (!value.StartsWith(expectedPrefix, comparisonType))
         {
             string userMessage = BuildUserMessageForExpectedPrefixExpressionAndValueExpression(message, expectedPrefixExpression, valueExpression);
@@ -144,8 +144,8 @@ public static void DoesNotStartWith([NotNull] string? notExpectedPrefix, [NotNul
     /// </exception>
     public static void DoesNotStartWith([NotNull] string? notExpectedPrefix, [NotNull] string? value, StringComparison comparisonType, string? message = "", [CallerArgumentExpression(nameof(notExpectedPrefix))] string notExpectedPrefixExpression = "", [CallerArgumentExpression(nameof(value))] string valueExpression = "")
     {
-        CheckParameterNotNull(value, "Assert.DoesNotStartWith", "value", string.Empty);
-        CheckParameterNotNull(notExpectedPrefix, "Assert.DoesNotStartWith", "notExpectedPrefix", string.Empty);
+        CheckParameterNotNull(value, "Assert.DoesNotStartWith", "value");
+        CheckParameterNotNull(notExpectedPrefix, "Assert.DoesNotStartWith", "notExpectedPrefix");
         if (value.StartsWith(notExpectedPrefix, comparisonType))
         {
             string userMessage = BuildUserMessageForNotExpectedPrefixExpressionAndValueExpression(message, notExpectedPrefixExpression, valueExpression);
diff --git a/src/TestFramework/TestFramework/Assertions/Assert.cs b/src/TestFramework/TestFramework/Assertions/Assert.cs
index 2035fbf618..61a2e56800 100644
--- a/src/TestFramework/TestFramework/Assertions/Assert.cs
+++ b/src/TestFramework/TestFramework/Assertions/Assert.cs
@@ -160,15 +160,11 @@ private static string BuildUserMessageForMinValueExpressionAndMaxValueExpression
     /// <param name="parameterName">
     /// parameter name.
     /// </param>
-    /// <param name="message">
-    /// message for the invalid parameter exception.
-    /// </param>
-    internal static void CheckParameterNotNull([NotNull] object? param, string assertionName, string parameterName, string? message)
+    internal static void CheckParameterNotNull([NotNull] object? param, string assertionName, string parameterName)
     {
         if (param == null)
         {
-            string userMessage = BuildUserMessage(message);
-            string finalMessage = string.Format(CultureInfo.CurrentCulture, FrameworkMessages.NullParameterToAssert, parameterName, userMessage);
+            string finalMessage = string.Format(CultureInfo.CurrentCulture, FrameworkMessages.NullParameterToAssert, parameterName);
             ThrowAssertFailed(assertionName, finalMessage);
         }
     }
diff --git a/src/TestFramework/TestFramework/Assertions/CollectionAssert.cs b/src/TestFramework/TestFramework/Assertions/CollectionAssert.cs
index de8c4c13c5..6be196fa94 100644
--- a/src/TestFramework/TestFramework/Assertions/CollectionAssert.cs
+++ b/src/TestFramework/TestFramework/Assertions/CollectionAssert.cs
@@ -69,7 +69,7 @@ public static void Contains([NotNull] ICollection? collection, object? element)
     /// </exception>
     public static void Contains([NotNull] ICollection? collection, object? element, string? message)
     {
-        Assert.CheckParameterNotNull(collection, "CollectionAssert.Contains", "collection", string.Empty);
+        Assert.CheckParameterNotNull(collection, "CollectionAssert.Contains", "collection");
 
         foreach (object? current in collection)
         {
@@ -120,7 +120,7 @@ public static void DoesNotContain([NotNull] ICollection? collection, object? ele
     /// </exception>
     public static void DoesNotContain([NotNull] ICollection? collection, object? element, string? message)
     {
-        Assert.CheckParameterNotNull(collection, "CollectionAssert.DoesNotContain", "collection", string.Empty);
+        Assert.CheckParameterNotNull(collection, "CollectionAssert.DoesNotContain", "collection");
 
         foreach (object? current in collection)
         {
@@ -160,7 +160,7 @@ public static void AllItemsAreNotNull([NotNull] ICollection? collection)
     /// </exception>
     public static void AllItemsAreNotNull([NotNull] ICollection? collection, string? message)
     {
-        Assert.CheckParameterNotNull(collection, "CollectionAssert.AllItemsAreNotNull", "collection", string.Empty);
+        Assert.CheckParameterNotNull(collection, "CollectionAssert.AllItemsAreNotNull", "collection");
         foreach (object? current in collection)
         {
             if (current == null)
@@ -202,7 +202,7 @@ public static void AllItemsAreUnique([NotNull] ICollection? collection)
     /// </exception>
     public static void AllItemsAreUnique([NotNull] ICollection? collection, string? message)
     {
-        Assert.CheckParameterNotNull(collection, "CollectionAssert.AllItemsAreUnique", "collection", string.Empty);
+        Assert.CheckParameterNotNull(collection, "CollectionAssert.AllItemsAreUnique", "collection");
 
         message = Assert.ReplaceNulls(message);
 
@@ -292,8 +292,8 @@ public static void IsSubsetOf([NotNull] ICollection? subset, [NotNull] ICollecti
     /// </exception>
     public static void IsSubsetOf([NotNull] ICollection? subset, [NotNull] ICollection? superset, string? message)
     {
-        Assert.CheckParameterNotNull(subset, "CollectionAssert.IsSubsetOf", "subset", string.Empty);
-        Assert.CheckParameterNotNull(superset, "CollectionAssert.IsSubsetOf", "superset", string.Empty);
+        Assert.CheckParameterNotNull(subset, "CollectionAssert.IsSubsetOf", "subset");
+        Assert.CheckParameterNotNull(superset, "CollectionAssert.IsSubsetOf", "superset");
         Tuple<bool, ICollection<object?>> isSubsetValue = IsSubsetOfHelper(subset, superset);
         if (!isSubsetValue.Item1)
         {
@@ -352,8 +352,8 @@ public static void IsNotSubsetOf([NotNull] ICollection? subset, [NotNull] IColle
     /// </exception>
     public static void IsNotSubsetOf([NotNull] ICollection? subset, [NotNull] ICollection? superset, string? message)
     {
-        Assert.CheckParameterNotNull(subset, "CollectionAssert.IsNotSubsetOf", "subset", string.Empty);
-        Assert.CheckParameterNotNull(superset, "CollectionAssert.IsNotSubsetOf", "superset", string.Empty);
+        Assert.CheckParameterNotNull(subset, "CollectionAssert.IsNotSubsetOf", "subset");
+        Assert.CheckParameterNotNull(superset, "CollectionAssert.IsNotSubsetOf", "superset");
         Tuple<bool, ICollection<object?>> isSubsetValue = IsSubsetOfHelper(subset, superset);
         if (isSubsetValue.Item1)
         {
@@ -471,7 +471,7 @@ public static void AreEquivalent<T>(
         [NotNullIfNotNull(nameof(actual))] IEnumerable<T?>? expected, [NotNullIfNotNull(nameof(expected))] IEnumerable<T?>? actual, [NotNull] IEqualityComparer<T>? comparer,
         string? message)
     {
-        Assert.CheckParameterNotNull(comparer, "Assert.AreCollectionsEqual", "comparer", string.Empty);
+        Assert.CheckParameterNotNull(comparer, "Assert.AreCollectionsEqual", "comparer");
 
         // Check whether one is null while the other is not.
         if (expected == null != (actual == null))
@@ -637,7 +637,7 @@ public static void AreNotEquivalent<T>(
         [NotNullIfNotNull(nameof(actual))] IEnumerable<T?>? notExpected, [NotNullIfNotNull(nameof(notExpected))] IEnumerable<T?>? actual, [NotNull] IEqualityComparer<T>? comparer,
         string? message)
     {
-        Assert.CheckParameterNotNull(comparer, "Assert.AreCollectionsEqual", "comparer", string.Empty);
+        Assert.CheckParameterNotNull(comparer, "Assert.AreCollectionsEqual", "comparer");
 
         // Check whether one is null while the other is not.
         if (notExpected == null != (actual == null))
@@ -738,8 +738,8 @@ public static void AllItemsAreInstancesOfType([NotNull] ICollection? collection,
     public static void AllItemsAreInstancesOfType(
         [NotNull] ICollection? collection, [NotNull] Type? expectedType, string? message)
     {
-        Assert.CheckParameterNotNull(collection, "CollectionAssert.AllItemsAreInstancesOfType", "collection", string.Empty);
-        Assert.CheckParameterNotNull(expectedType, "CollectionAssert.AllItemsAreInstancesOfType", "expectedType", string.Empty);
+        Assert.CheckParameterNotNull(collection, "CollectionAssert.AllItemsAreInstancesOfType", "collection");
+        Assert.CheckParameterNotNull(expectedType, "CollectionAssert.AllItemsAreInstancesOfType", "expectedType");
         int i = 0;
         foreach (object? element in collection)
         {
@@ -1177,7 +1177,7 @@ private static bool FindMismatchedElement<T>(IEnumerable<T?> expected, IEnumerab
     private static bool AreCollectionsEqual(ICollection? expected, ICollection? actual, [NotNull] IComparer? comparer,
         ref string reason)
     {
-        Assert.CheckParameterNotNull(comparer, "Assert.AreCollectionsEqual", "comparer", string.Empty);
+        Assert.CheckParameterNotNull(comparer, "Assert.AreCollectionsEqual", "comparer");
         if (object.ReferenceEquals(expected, actual))
         {
             reason = string.Format(CultureInfo.CurrentCulture, FrameworkMessages.BothCollectionsSameReference, string.Empty);
diff --git a/src/TestFramework/TestFramework/Assertions/StringAssert.cs b/src/TestFramework/TestFramework/Assertions/StringAssert.cs
index c54b83bf60..b2e36625ec 100644
--- a/src/TestFramework/TestFramework/Assertions/StringAssert.cs
+++ b/src/TestFramework/TestFramework/Assertions/StringAssert.cs
@@ -116,8 +116,8 @@ public static void Contains([NotNull] string? value, [NotNull] string? substring
     /// </exception>
     public static void Contains([NotNull] string? value, [NotNull] string? substring, StringComparison comparisonType, string? message)
     {
-        Assert.CheckParameterNotNull(value, "StringAssert.Contains", "value", string.Empty);
-        Assert.CheckParameterNotNull(substring, "StringAssert.Contains", "substring", string.Empty);
+        Assert.CheckParameterNotNull(value, "StringAssert.Contains", "value");
+        Assert.CheckParameterNotNull(substring, "StringAssert.Contains", "substring");
         if (value.IndexOf(substring, comparisonType) < 0)
         {
             string userMessage = Assert.BuildUserMessage(message);
@@ -213,8 +213,8 @@ public static void StartsWith([NotNull] string? value, [NotNull] string? substri
     /// </exception>
     public static void StartsWith([NotNull] string? value, [NotNull] string? substring, StringComparison comparisonType, string? message)
     {
-        Assert.CheckParameterNotNull(value, "StringAssert.StartsWith", "value", string.Empty);
-        Assert.CheckParameterNotNull(substring, "StringAssert.StartsWith", "substring", string.Empty);
+        Assert.CheckParameterNotNull(value, "StringAssert.StartsWith", "value");
+        Assert.CheckParameterNotNull(substring, "StringAssert.StartsWith", "substring");
         if (!value.StartsWith(substring, comparisonType))
         {
             string userMessage = Assert.BuildUserMessage(message);
@@ -310,8 +310,8 @@ public static void EndsWith([NotNull] string? value, [NotNull] string? substring
     /// </exception>
     public static void EndsWith([NotNull] string? value, [NotNull] string? substring, StringComparison comparisonType, string? message)
     {
-        Assert.CheckParameterNotNull(value, "StringAssert.EndsWith", "value", string.Empty);
-        Assert.CheckParameterNotNull(substring, "StringAssert.EndsWith", "substring", string.Empty);
+        Assert.CheckParameterNotNull(value, "StringAssert.EndsWith", "value");
+        Assert.CheckParameterNotNull(substring, "StringAssert.EndsWith", "substring");
         if (!value.EndsWith(substring, comparisonType))
         {
             string userMessage = Assert.BuildUserMessage(message);
@@ -364,8 +364,8 @@ public static void Matches([NotNull] string? value, [NotNull] Regex? pattern)
     /// </exception>
     public static void Matches([NotNull] string? value, [NotNull] Regex? pattern, string? message)
     {
-        Assert.CheckParameterNotNull(value, "StringAssert.Matches", "value", string.Empty);
-        Assert.CheckParameterNotNull(pattern, "StringAssert.Matches", "pattern", string.Empty);
+        Assert.CheckParameterNotNull(value, "StringAssert.Matches", "value");
+        Assert.CheckParameterNotNull(pattern, "StringAssert.Matches", "pattern");
 
         if (!pattern.IsMatch(value))
         {
@@ -415,8 +415,8 @@ public static void DoesNotMatch([NotNull] string? value, [NotNull] Regex? patter
     /// </exception>
     public static void DoesNotMatch([NotNull] string? value, [NotNull] Regex? pattern, string? message)
     {
-        Assert.CheckParameterNotNull(value, "StringAssert.DoesNotMatch", "value", string.Empty);
-        Assert.CheckParameterNotNull(pattern, "StringAssert.DoesNotMatch", "pattern", string.Empty);
+        Assert.CheckParameterNotNull(value, "StringAssert.DoesNotMatch", "value");
+        Assert.CheckParameterNotNull(pattern, "StringAssert.DoesNotMatch", "pattern");
 
         if (pattern.IsMatch(value))
         {
diff --git a/src/TestFramework/TestFramework/PublicAPI/PublicAPI.Unshipped.txt b/src/TestFramework/TestFramework/PublicAPI/PublicAPI.Unshipped.txt
index 0a398540b2..1e42a88f47 100644
--- a/src/TestFramework/TestFramework/PublicAPI/PublicAPI.Unshipped.txt
+++ b/src/TestFramework/TestFramework/PublicAPI/PublicAPI.Unshipped.txt
@@ -1,3 +1,3 @@
 #nullable enable
-static Microsoft.VisualStudio.TestTools.UnitTesting.Assert.ContainsSingle(System.Collections.IEnumerable! collection, string? message = "", string! collectionExpression = "") -> object!
-static Microsoft.VisualStudio.TestTools.UnitTesting.Assert.ContainsSingle(System.Func<object!, bool>! predicate, System.Collections.IEnumerable! collection, string? message = "", string! predicateExpression = "", string! collectionExpression = "") -> object!
+static Microsoft.VisualStudio.TestTools.UnitTesting.Assert.ContainsSingle(System.Collections.IEnumerable! collection, string? message = "", string! collectionExpression = "") -> object?
+static Microsoft.VisualStudio.TestTools.UnitTesting.Assert.ContainsSingle(System.Func<object!, bool>! predicate, System.Collections.IEnumerable! collection, string? message = "", string! predicateExpression = "", string! collectionExpression = "") -> object?
diff --git a/src/TestFramework/TestFramework/Resources/FrameworkMessages.resx b/src/TestFramework/TestFramework/Resources/FrameworkMessages.resx
index 6c020b112d..b31ee2ee76 100644
--- a/src/TestFramework/TestFramework/Resources/FrameworkMessages.resx
+++ b/src/TestFramework/TestFramework/Resources/FrameworkMessages.resx
@@ -230,7 +230,7 @@ Actual: {2}</value>
     </value>
   </data>
   <data name="NullParameterToAssert" xml:space="preserve">
-    <value>The parameter '{0}' is invalid. The value cannot be null. {1}.</value>
+    <value>The parameter '{0}' is invalid. The value cannot be null.</value>
   </data>
   <data name="NumberOfElementsDiff" xml:space="preserve">
     <value>Different number of elements.</value>
diff --git a/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.cs.xlf b/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.cs.xlf
index eab65aa221..a25c467f23 100644
--- a/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.cs.xlf
+++ b/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.cs.xlf
@@ -314,8 +314,8 @@ Skutečnost: {2}</target>
         <note />
       </trans-unit>
       <trans-unit id="NullParameterToAssert">
-        <source>The parameter '{0}' is invalid. The value cannot be null. {1}.</source>
-        <target state="translated">Parametr '{0}' je neplatný. Hodnota nemůže být null. {1}.</target>
+        <source>The parameter '{0}' is invalid. The value cannot be null.</source>
+        <target state="translated">Parametr '{0}' je neplatný. Hodnota nemůže být null.</target>
         <note></note>
       </trans-unit>
       <trans-unit id="NumberOfElementsDiff">
diff --git a/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.de.xlf b/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.de.xlf
index f4afaa9934..e8804d2f3e 100644
--- a/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.de.xlf
+++ b/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.de.xlf
@@ -314,8 +314,8 @@ Tatsächlich: {2}</target>
         <note />
       </trans-unit>
       <trans-unit id="NullParameterToAssert">
-        <source>The parameter '{0}' is invalid. The value cannot be null. {1}.</source>
-        <target state="translated">Der {0}-Parameter ist ungültig. Der Wert kann nicht NULL sein. {1}.</target>
+        <source>The parameter '{0}' is invalid. The value cannot be null.</source>
+        <target state="translated">Der {0}-Parameter ist ungültig. Der Wert kann nicht NULL sein.</target>
         <note></note>
       </trans-unit>
       <trans-unit id="NumberOfElementsDiff">
diff --git a/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.es.xlf b/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.es.xlf
index c1dbf79e36..2ea479ed93 100644
--- a/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.es.xlf
+++ b/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.es.xlf
@@ -314,8 +314,8 @@ Real: {2}</target>
         <note />
       </trans-unit>
       <trans-unit id="NullParameterToAssert">
-        <source>The parameter '{0}' is invalid. The value cannot be null. {1}.</source>
-        <target state="translated">El parámetro '{0}' no es válido. El valor no puede ser null. {1}.</target>
+        <source>The parameter '{0}' is invalid. The value cannot be null.</source>
+        <target state="translated">El parámetro '{0}' no es válido. El valor no puede ser null.</target>
         <note></note>
       </trans-unit>
       <trans-unit id="NumberOfElementsDiff">
diff --git a/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.fr.xlf b/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.fr.xlf
index 1a61f44795..23bbfb22af 100644
--- a/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.fr.xlf
+++ b/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.fr.xlf
@@ -314,8 +314,8 @@ Réel : {2}</target>
         <note />
       </trans-unit>
       <trans-unit id="NullParameterToAssert">
-        <source>The parameter '{0}' is invalid. The value cannot be null. {1}.</source>
-        <target state="translated">Le paramètre '{0}' n'est pas valide. La valeur ne peut pas être null. {1}.</target>
+        <source>The parameter '{0}' is invalid. The value cannot be null.</source>
+        <target state="translated">Le paramètre '{0}' n'est pas valide. La valeur ne peut pas être null.</target>
         <note></note>
       </trans-unit>
       <trans-unit id="NumberOfElementsDiff">
diff --git a/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.it.xlf b/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.it.xlf
index 0506e80a37..ebeb2c95e6 100644
--- a/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.it.xlf
+++ b/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.it.xlf
@@ -314,8 +314,8 @@ Effettivo: {2}</target>
         <note />
       </trans-unit>
       <trans-unit id="NullParameterToAssert">
-        <source>The parameter '{0}' is invalid. The value cannot be null. {1}.</source>
-        <target state="translated">Il parametro '{0}' non è valido. Il valore non può essere Null. {1}.</target>
+        <source>The parameter '{0}' is invalid. The value cannot be null.</source>
+        <target state="translated">Il parametro '{0}' non è valido. Il valore non può essere Null.</target>
         <note></note>
       </trans-unit>
       <trans-unit id="NumberOfElementsDiff">
diff --git a/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.ja.xlf b/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.ja.xlf
index 7f9a7f8ed8..e7afd5d6c9 100644
--- a/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.ja.xlf
+++ b/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.ja.xlf
@@ -314,8 +314,8 @@ Actual: {2}</source>
         <note />
       </trans-unit>
       <trans-unit id="NullParameterToAssert">
-        <source>The parameter '{0}' is invalid. The value cannot be null. {1}.</source>
-        <target state="translated">パラメーター '{0}' は無効です。値を null にすることはできません。{1}。</target>
+        <source>The parameter '{0}' is invalid. The value cannot be null.</source>
+        <target state="translated">パラメーター '{0}' は無効です。値を null にすることはできません。</target>
         <note></note>
       </trans-unit>
       <trans-unit id="NumberOfElementsDiff">
diff --git a/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.ko.xlf b/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.ko.xlf
index a650895266..45b953dab4 100644
--- a/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.ko.xlf
+++ b/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.ko.xlf
@@ -314,8 +314,8 @@ Actual: {2}</source>
         <note />
       </trans-unit>
       <trans-unit id="NullParameterToAssert">
-        <source>The parameter '{0}' is invalid. The value cannot be null. {1}.</source>
-        <target state="translated">'{0}' 매개 변수가 잘못되었습니다. 이 값은 null일 수 없습니다. {1}.</target>
+        <source>The parameter '{0}' is invalid. The value cannot be null.</source>
+        <target state="translated">'{0}' 매개 변수가 잘못되었습니다. 이 값은 null일 수 없습니다.</target>
         <note></note>
       </trans-unit>
       <trans-unit id="NumberOfElementsDiff">
diff --git a/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.pl.xlf b/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.pl.xlf
index 1e73855a86..5d3191394e 100644
--- a/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.pl.xlf
+++ b/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.pl.xlf
@@ -314,8 +314,8 @@ Rzeczywiste: {2}</target>
         <note />
       </trans-unit>
       <trans-unit id="NullParameterToAssert">
-        <source>The parameter '{0}' is invalid. The value cannot be null. {1}.</source>
-        <target state="translated">Parametr „{0}” jest nieprawidłowy. Wartość nie może być równa null. {1}.</target>
+        <source>The parameter '{0}' is invalid. The value cannot be null.</source>
+        <target state="translated">Parametr „{0}” jest nieprawidłowy. Wartość nie może być równa null.</target>
         <note></note>
       </trans-unit>
       <trans-unit id="NumberOfElementsDiff">
diff --git a/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.pt-BR.xlf b/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.pt-BR.xlf
index ae0177763d..ce04ba5c04 100644
--- a/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.pt-BR.xlf
+++ b/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.pt-BR.xlf
@@ -314,8 +314,8 @@ Real: {2}</target>
         <note />
       </trans-unit>
       <trans-unit id="NullParameterToAssert">
-        <source>The parameter '{0}' is invalid. The value cannot be null. {1}.</source>
-        <target state="translated">O parâmetro '{0}' é inválido. O valor não pode ser nulo. {1}.</target>
+        <source>The parameter '{0}' is invalid. The value cannot be null.</source>
+        <target state="translated">O parâmetro '{0}' é inválido. O valor não pode ser nulo.</target>
         <note></note>
       </trans-unit>
       <trans-unit id="NumberOfElementsDiff">
diff --git a/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.ru.xlf b/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.ru.xlf
index 23d579aea8..af62e296b8 100644
--- a/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.ru.xlf
+++ b/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.ru.xlf
@@ -314,8 +314,8 @@ Actual: {2}</source>
         <note />
       </trans-unit>
       <trans-unit id="NullParameterToAssert">
-        <source>The parameter '{0}' is invalid. The value cannot be null. {1}.</source>
-        <target state="translated">Параметр "{0}" является недопустимым. Значение не может быть NULL. {1}.</target>
+        <source>The parameter '{0}' is invalid. The value cannot be null.</source>
+        <target state="translated">Параметр "{0}" является недопустимым. Значение не может быть NULL.</target>
         <note></note>
       </trans-unit>
       <trans-unit id="NumberOfElementsDiff">
diff --git a/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.tr.xlf b/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.tr.xlf
index 8621c19d21..569beb77c5 100644
--- a/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.tr.xlf
+++ b/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.tr.xlf
@@ -314,8 +314,8 @@ Gerçekte olan: {2}</target>
         <note />
       </trans-unit>
       <trans-unit id="NullParameterToAssert">
-        <source>The parameter '{0}' is invalid. The value cannot be null. {1}.</source>
-        <target state="translated">'{0}' parametresi geçersiz. Değer null olamaz. {1}.</target>
+        <source>The parameter '{0}' is invalid. The value cannot be null.</source>
+        <target state="translated">'{0}' parametresi geçersiz. Değer null olamaz.</target>
         <note></note>
       </trans-unit>
       <trans-unit id="NumberOfElementsDiff">
diff --git a/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.zh-Hans.xlf b/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.zh-Hans.xlf
index 8587ad71a8..7161aa6780 100644
--- a/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.zh-Hans.xlf
+++ b/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.zh-Hans.xlf
@@ -314,8 +314,8 @@ Actual: {2}</source>
         <note />
       </trans-unit>
       <trans-unit id="NullParameterToAssert">
-        <source>The parameter '{0}' is invalid. The value cannot be null. {1}.</source>
-        <target state="translated">参数“{0}”无效。值不能为 NULL。{1}。</target>
+        <source>The parameter '{0}' is invalid. The value cannot be null.</source>
+        <target state="translated">>参数“{0}”无效。值不能为 NULL。</target>
         <note></note>
       </trans-unit>
       <trans-unit id="NumberOfElementsDiff">
diff --git a/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.zh-Hant.xlf b/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.zh-Hant.xlf
index 18d8fe9c41..77b31c0f61 100644
--- a/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.zh-Hant.xlf
+++ b/src/TestFramework/TestFramework/Resources/xlf/FrameworkMessages.zh-Hant.xlf
@@ -314,8 +314,8 @@ Actual: {2}</source>
         <note />
       </trans-unit>
       <trans-unit id="NullParameterToAssert">
-        <source>The parameter '{0}' is invalid. The value cannot be null. {1}.</source>
-        <target state="translated">參數 '{0}' 無效。此值不可為 null。{1}。</target>
+        <source>The parameter '{0}' is invalid. The value cannot be null.</source>
+        <target state="translated">參數 '{0}' 無效。此值不可為 null。</target>
         <note></note>
       </trans-unit>
       <trans-unit id="NumberOfElementsDiff">
diff --git a/test/UnitTests/TestFramework.UnitTests/Assertions/AssertTests.Contains.cs b/test/UnitTests/TestFramework.UnitTests/Assertions/AssertTests.Contains.cs
index 8d35a540a8..374b04b766 100644
--- a/test/UnitTests/TestFramework.UnitTests/Assertions/AssertTests.Contains.cs
+++ b/test/UnitTests/TestFramework.UnitTests/Assertions/AssertTests.Contains.cs
@@ -417,7 +417,7 @@ public void Contains_ValueExpected_ItemDoesNotExist_ThrowsException()
         Action action = () => Assert.Contains(20, collection, "Item 20 not found");
 
         // Assert
-        action.Should().Throw<AssertFailedException>().WithMessage("*20*");
+        action.Should().Throw<AssertFailedException>().WithMessage("Assert.Contains failed. Expected collection to contain the specified item. 'expected' expression: '20', 'collection' expression: 'collection'. Item 20 not found");
     }
 
     /// <summary>
@@ -528,7 +528,7 @@ public void Contains_WithComparer_ItemDoesNotExist_ThrowsException()
         Action action = () => Assert.Contains("cherry", collection, comparer, "Missing cherry");
 
         // Assert
-        action.Should().Throw<AssertFailedException>().WithMessage("*cherry*");
+        action.Should().Throw<AssertFailedException>().WithMessage("Assert.Contains failed. Expected collection to contain the specified item. 'expected' expression: '\"cherry\"', 'collection' expression: 'collection'. Missing cherry");
     }
 
     /// <summary>
@@ -574,7 +574,7 @@ public void Contains_Predicate_NoItemMatches_ThrowsException()
         Action action = () => Assert.Contains(IsEven, collection, "No even number found");
 
         // Assert
-        action.Should().Throw<AssertFailedException>().WithMessage("*even*");
+        action.Should().Throw<AssertFailedException>().WithMessage("Assert.Contains failed. Expected at least one item to match the predicate. 'predicate' expression: 'IsEven', 'collection' expression: 'collection'. No even number found");
     }
 
     /// <summary>
@@ -590,7 +590,7 @@ public void Contains_InNonGenericCollection_Predicate_NoItemMatches_ThrowsExcept
         Action action = () => Assert.Contains(IsEven, collection, "No even number found");
 
         // Assert
-        action.Should().Throw<AssertFailedException>().WithMessage("*even*");
+        action.Should().Throw<AssertFailedException>().WithMessage("Assert.Contains failed. Expected at least one item to match the predicate. 'predicate' expression: 'IsEven', 'collection' expression: 'collection'. No even number found");
     }
 
     /// <summary>
@@ -623,7 +623,7 @@ public void Contains_StringVersion_SubstringNotPresent_ThrowsException()
         Action action = () => Assert.Contains(substring, value, StringComparison.Ordinal, "Missing substring");
 
         // Assert
-        action.Should().Throw<AssertFailedException>().WithMessage("*lazy*");
+        action.Should().Throw<AssertFailedException>().WithMessage("Assert.Contains failed. String 'The quick brown fox' does not contain string 'lazy'. 'substring' expression: 'substring', 'value' expression: 'value'. Missing substring.");
     }
 
     public void Contains_HashSetWithCustomComparer_ItemExists_DoesNotThrow()
@@ -636,6 +636,275 @@ public void Contains_HashSetWithCustomComparer_ItemExists_DoesNotThrow()
         action();
     }
 
+    /// <summary>
+    /// Tests the Contains method (non-generic) when collection is null.
+    /// Expects an AssertFailedException.
+    /// </summary>
+    public void Contains_InNonGenericCollection_NullCollection_ThrowsException()
+    {
+        // Arrange
+        IEnumerable collection = null!;
+
+        // Act
+        Action action = () => Assert.Contains(1, collection);
+
+        // Assert
+        action.Should().Throw<AssertFailedException>().WithMessage("Assert.Contains failed. The parameter 'collection' is invalid. The value cannot be null.");
+    }
+
+    /// <summary>
+    /// Tests the Contains method (non-generic) with comparer when collection is null.
+    /// Expects an AssertFailedException.
+    /// </summary>
+    public void Contains_InNonGenericCollection_WithComparer_NullCollection_ThrowsException()
+    {
+        // Arrange
+        IEnumerable collection = null!;
+        EqualityComparer<object> comparer = EqualityComparer<object>.Default;
+
+        // Act
+        Action action = () => Assert.Contains(1, collection, comparer);
+
+        // Assert
+        action.Should().Throw<AssertFailedException>().WithMessage("Assert.Contains failed. The parameter 'collection' is invalid. The value cannot be null.");
+    }
+
+    /// <summary>
+    /// Tests the Contains method (non-generic) with comparer when item exists.
+    /// </summary>
+    public void Contains_InNonGenericCollection_WithComparer_ItemExists_DoesNotThrow()
+    {
+        // Arrange
+        var collection = new ArrayList { "apple", "BANANA", "cherry" };
+        StringComparer comparer = StringComparer.OrdinalIgnoreCase;
+
+        // Act
+        Action action = () => Assert.Contains("banana", collection, comparer);
+
+        // Assert
+        action.Should().NotThrow<AssertFailedException>();
+    }
+
+    /// <summary>
+    /// Tests the Contains method (non-generic) with comparer when item does not exist.
+    /// Expects an AssertFailedException.
+    /// </summary>
+    public void Contains_InNonGenericCollection_WithComparer_ItemDoesNotExist_ThrowsException()
+    {
+        // Arrange
+        var collection = new ArrayList { "apple", "cherry" };
+        StringComparer comparer = StringComparer.OrdinalIgnoreCase;
+
+        // Act
+        Action action = () => Assert.Contains("banana", collection, comparer);
+
+        // Assert
+        action.Should().Throw<AssertFailedException>().WithMessage("Assert.Contains failed. Expected collection to contain the specified item. 'expected' expression: '\"banana\"', 'collection' expression: 'collection'.");
+    }
+
+    /// <summary>
+    /// Tests the Contains method (non-generic) with predicate when collection is null.
+    /// Expects an AssertFailedException.
+    /// </summary>
+    public void Contains_InNonGenericCollection_Predicate_NullCollection_ThrowsException()
+    {
+        // Arrange
+        IEnumerable collection = null!;
+
+        // Act
+        Action action = () => Assert.Contains(Predicate, collection);
+
+        // Assert
+        action.Should().Throw<AssertFailedException>().WithMessage("Assert.Contains failed. The parameter 'collection' is invalid. The value cannot be null.");
+
+        // Local functions
+        static bool Predicate(object? x) => x is int i && i > 5;
+    }
+
+    /// <summary>
+    /// Tests the Contains method (non-generic) with null predicate.
+    /// Expects an AssertFailedException.
+    /// </summary>
+    public void Contains_InNonGenericCollection_NullPredicate_ThrowsException()
+    {
+        // Arrange
+        var collection = new ArrayList { 1, 2, 3 };
+        Func<object?, bool> predicate = null!;
+
+        // Act
+        Action action = () => Assert.Contains(predicate, collection);
+
+        // Assert
+        action.Should().Throw<AssertFailedException>().WithMessage("Assert.Contains failed. The parameter 'predicate' is invalid. The value cannot be null.");
+    }
+
+    /// <summary>
+    /// Tests the Contains method (non-generic) with collection containing multiple nulls when searching for null.
+    /// </summary>
+    public void Contains_InNonGenericCollection_MultipleNulls_SearchingForNull_DoesNotThrow()
+    {
+        // Arrange
+        var collection = new ArrayList { null, 1, null, 2 };
+
+        // Act
+        Action action = () => Assert.Contains(x => x is null, collection);
+
+        // Assert
+        action.Should().NotThrow();
+    }
+
+    /// <summary>
+    /// Tests the string Contains method when substring is null.
+    /// Expects an AssertFailedException.
+    /// </summary>
+    public void Contains_String_NullSubstring_ThrowsException()
+    {
+        // Arrange
+        string substring = null!;
+        string value = "test value";
+
+        // Act
+        Action action = () => Assert.Contains(substring, value);
+
+        // Assert
+        action.Should().Throw<AssertFailedException>().WithMessage("Assert.Contains failed. The parameter 'substring' is invalid. The value cannot be null.");
+    }
+
+    /// <summary>
+    /// Tests the string Contains method when value is null.
+    /// Expects an AssertFailedException.
+    /// </summary>
+    public void Contains_String_NullValue_ThrowsException()
+    {
+        // Arrange
+        string substring = "test";
+        string value = null!;
+
+        // Act
+        Action action = () => Assert.Contains(substring, value);
+
+        // Assert
+        action.Should().Throw<AssertFailedException>().WithMessage("Assert.Contains failed. The parameter 'value' is invalid. The value cannot be null.");
+    }
+
+    /// <summary>
+    /// Tests the string Contains method when both substring and value are null.
+    /// Expects an AssertFailedException.
+    /// </summary>
+    public void Contains_String_BothNull_ThrowsException()
+    {
+        // Arrange
+        string substring = null!;
+        string value = null!;
+
+        // Act
+        Action action = () => Assert.Contains(substring, value);
+
+        // Assert
+        action.Should().Throw<AssertFailedException>().WithMessage("Assert.Contains failed. The parameter 'value' is invalid. The value cannot be null.");
+    }
+
+    /// <summary>
+    /// Tests the string Contains method with empty substring.
+    /// </summary>
+    public void Contains_String_EmptySubstring_DoesNotThrow()
+    {
+        // Arrange
+        string substring = string.Empty;
+        string value = "test value";
+
+        // Act
+        Action action = () => Assert.Contains(substring, value);
+
+        // Assert
+        // Empty string is contained in any string
+        action.Should().NotThrow<AssertFailedException>();
+    }
+
+    /// <summary>
+    /// Tests the string Contains method with empty value.
+    /// </summary>
+    public void Contains_String_EmptyValue_WithNonEmptySubstring_ThrowsException()
+    {
+        // Arrange
+        string substring = "test";
+        string value = string.Empty;
+
+        // Act
+        Action action = () => Assert.Contains(substring, value);
+
+        // Assert
+        action.Should().Throw<AssertFailedException>().WithMessage("Assert.Contains failed. String '' does not contain string 'test'. 'substring' expression: 'substring', 'value' expression: 'value'..");
+    }
+
+    /// <summary>
+    /// Tests the string Contains method with both empty strings.
+    /// </summary>
+    public void Contains_String_BothEmpty_DoesNotThrow()
+    {
+        // Arrange
+        string substring = string.Empty;
+        string value = string.Empty;
+
+        // Act
+        Action action = () => Assert.Contains(substring, value);
+
+        // Assert
+        // Empty string contains empty string
+        action.Should().NotThrow<AssertFailedException>();
+    }
+
+    /// <summary>
+    /// Tests the string Contains method with StringComparison when substring is null.
+    /// Expects an AssertFailedException.
+    /// </summary>
+    public void Contains_String_WithComparison_NullSubstring_ThrowsException()
+    {
+        // Arrange
+        string substring = null!;
+        string value = "test value";
+
+        // Act
+        Action action = () => Assert.Contains(substring, value, StringComparison.OrdinalIgnoreCase);
+
+        // Assert
+        action.Should().Throw<AssertFailedException>().WithMessage("Assert.Contains failed. The parameter 'substring' is invalid. The value cannot be null.");
+    }
+
+    /// <summary>
+    /// Tests the string Contains method with StringComparison when value is null.
+    /// Expects an AssertFailedException.
+    /// </summary>
+    public void Contains_String_WithComparison_NullValue_ThrowsException()
+    {
+        // Arrange
+        string substring = "test";
+        string value = null!;
+
+        // Act
+        Action action = () => Assert.Contains(substring, value, StringComparison.OrdinalIgnoreCase);
+
+        // Assert
+        action.Should().Throw<AssertFailedException>().WithMessage("Assert.Contains failed. The parameter 'value' is invalid. The value cannot be null.");
+    }
+
+    /// <summary>
+    /// Tests the Contains method (non-generic) with null comparer.
+    /// Expects an AssertFailedException.
+    /// </summary>
+    public void Contains_InNonGenericCollection_WithComparer_NullComparer_ThrowsException()
+    {
+        // Arrange
+        var collection = new ArrayList { "apple", "banana" };
+        IEqualityComparer comparer = null!;
+
+        // Act
+        Action action = () => Assert.Contains("apple", collection, comparer);
+
+        // Assert
+        action.Should().Throw<AssertFailedException>().WithMessage("Assert.Contains failed. The parameter 'comparer' is invalid. The value cannot be null.");
+    }
+
     #endregion
 
     #region DoesNotContain Tests
@@ -668,7 +937,7 @@ public void DoesNotContain_ValueExpected_ItemPresent_ThrowsException()
         Action action = () => Assert.DoesNotContain(10, collection, "Item 10 should not be found");
 
         // Assert
-        action.Should().Throw<AssertFailedException>().WithMessage("*10*");
+        action.Should().Throw<AssertFailedException>().WithMessage("Assert.DoesNotContain failed. Expected collection to not contain the specified item. 'notExpected' expression: '10', 'collection' expression: 'collection'. Item 10 should not be found");
     }
 
     /// <summary>
@@ -699,7 +968,7 @@ public void DoesNotContain_InNonGenericCollection_ValueExpected_ItemPresent_Thro
         Action action = () => Assert.DoesNotContain(10, collection, "Assert.DoesNotContain failed. Expected collection to not contain the specified item. Item {0} should not be found");
 
         // Assert
-        action.Should().Throw<AssertFailedException>().WithMessage("*Assert.DoesNotContain failed. Expected collection to not contain the specified item. Item {0} should not be found*");
+        action.Should().Throw<AssertFailedException>().WithMessage("Assert.DoesNotContain failed. Expected collection to not contain the specified item. 'notExpected' expression: '10', 'collection' expression: 'collection'. Assert.DoesNotContain failed. Expected collection to not contain the specified item. Item {0} should not be found");
     }
 
     /// <summary>
@@ -748,7 +1017,7 @@ public void DoesNotContain_WithComparer_ItemPresent_ThrowsException()
         Action action = () => Assert.DoesNotContain("APPLE", collection, comparer, "Unexpected \"APPLE\"");
 
         // Assert
-        action.Should().Throw<AssertFailedException>().WithMessage("*APPLE*");
+        action.Should().Throw<AssertFailedException>().WithMessage("Assert.DoesNotContain failed. Expected collection to not contain the specified item. 'notExpected' expression: '\"APPLE\"', 'collection' expression: 'collection'. Unexpected \"APPLE\"");
     }
 
     /// <summary>
@@ -765,7 +1034,7 @@ public void DoesNotContain_InNonGenericCollection_WithComparer_ItemPresent_Throw
         Action action = () => Assert.DoesNotContain("APPLE", collection, comparer, "APPLE");
 
         // Assert
-        action.Should().Throw<AssertFailedException>().WithMessage("*APPLE*");
+        action.Should().Throw<AssertFailedException>().WithMessage("Assert.DoesNotContain failed. Expected collection to not contain the specified item. 'notExpected' expression: '\"APPLE\"', 'collection' expression: 'collection'. APPLE");
     }
 
     /// <summary>
@@ -811,7 +1080,7 @@ public void DoesNotContain_Predicate_AtLeastOneItemMatches_ThrowsException()
         Action action = () => Assert.DoesNotContain(IsEven, collection, "An even number exists");
 
         // Assert
-        action.Should().Throw<AssertFailedException>().WithMessage("*even*");
+        action.Should().Throw<AssertFailedException>().WithMessage("Assert.DoesNotContain failed. Expected no items to match the predicate. 'predicate' expression: 'IsEven', 'collection' expression: 'collection'. An even number exists");
     }
 
     /// <summary>
@@ -827,7 +1096,7 @@ public void DoesNotContain_InNonGenericCollection_Predicate_AtLeastOneItemMatche
         Action action = () => Assert.DoesNotContain(IsEven, collection, "An even number exists");
 
         // Assert
-        action.Should().Throw<AssertFailedException>().WithMessage("*even*");
+        action.Should().Throw<AssertFailedException>().WithMessage("Assert.DoesNotContain failed. Expected no items to match the predicate. 'predicate' expression: 'IsEven', 'collection' expression: 'collection'. An even number exists");
     }
 
     /// <summary>
@@ -860,7 +1129,7 @@ public void DoesNotContain_StringVersion_SubstringPresent_ThrowsException()
         Action action = () => Assert.DoesNotContain(substring, value, StringComparison.Ordinal, "Unexpected substring");
 
         // Assert
-        action.Should().Throw<AssertFailedException>().WithMessage("*brown*");
+        action.Should().Throw<AssertFailedException>().WithMessage("Assert.DoesNotContain failed. String 'The quick brown fox' does contain string 'brown'. 'substring' expression: 'substring', 'value' expression: 'value'. Unexpected substring.");
     }
 
     /// <summary>
@@ -895,7 +1164,7 @@ public void DoesNotContain_StringWithComparisonAndMessage_SubstringPresent_Throw
         Action action = () => Assert.DoesNotContain(substring, value, StringComparison.OrdinalIgnoreCase, "Found unexpected substring");
 
         // Assert
-        action.Should().Throw<AssertFailedException>().WithMessage("*Found unexpected substring*");
+        action.Should().Throw<AssertFailedException>().WithMessage("Assert.DoesNotContain failed. String 'The quick brown fox' does contain string 'BROWN'. 'substring' expression: 'substring', 'value' expression: 'value'. Found unexpected substring.");
     }
 
     /// <summary>
@@ -928,7 +1197,7 @@ public void DoesNotContain_StringSimpleOverload_SubstringPresent_ThrowsException
         Action action = () => Assert.DoesNotContain(substring, value);
 
         // Assert
-        action.Should().Throw<AssertFailedException>().WithMessage("*brown*");
+        action.Should().Throw<AssertFailedException>().WithMessage("Assert.DoesNotContain failed. String 'The quick brown fox' does contain string 'brown'. 'substring' expression: 'substring', 'value' expression: 'value'..");
     }
 
     /// <summary>
@@ -961,7 +1230,161 @@ public void DoesNotContain_StringWithMessageOnly_SubstringPresent_ThrowsExceptio
         Action action = () => Assert.DoesNotContain(substring, value, "Found unexpected substring");
 
         // Assert
-        action.Should().Throw<AssertFailedException>().WithMessage("*Found unexpected substring*");
+        action.Should().Throw<AssertFailedException>().WithMessage("Assert.DoesNotContain failed. String 'The quick brown fox' does contain string 'brown'. 'substring' expression: 'substring', 'value' expression: 'value'. Found unexpected substring.");
+    }
+
+    /// <summary>
+    /// Tests the DoesNotContain method (non-generic) when collection is null.
+    /// Expects an AssertFailedException.
+    /// </summary>
+    public void DoesNotContain_InNonGenericCollection_NullCollection_ThrowsException()
+    {
+        // Arrange
+        IEnumerable collection = null!;
+
+        // Act
+        Action action = () => Assert.DoesNotContain(1, collection);
+
+        // Assert
+        action.Should().Throw<AssertFailedException>().WithMessage("Assert.DoesNotContain failed. The parameter 'collection' is invalid. The value cannot be null.");
+    }
+
+    /// <summary>
+    /// Tests the DoesNotContain method (non-generic) with comparer when collection is null.
+    /// Expects an ArgumentNullException.
+    /// </summary>
+    public void DoesNotContain_InNonGenericCollection_WithComparer_NullCollection_ThrowsException()
+    {
+        // Arrange
+        IEnumerable collection = null!;
+        EqualityComparer<object> comparer = EqualityComparer<object>.Default;
+
+        // Act
+        Action action = () => Assert.DoesNotContain(1, collection, comparer);
+
+        // Assert
+        action.Should().Throw<AssertFailedException>().WithMessage("Assert.DoesNotContain failed. The parameter 'collection' is invalid. The value cannot be null.");
+    }
+
+    /// <summary>
+    /// Tests the DoesNotContain method (non-generic) with null comparer.
+    /// Expects an ArgumentNullException.
+    /// </summary>
+    public void DoesNotContain_InNonGenericCollection_WithComparer_NullComparer_ThrowsException()
+    {
+        // Arrange
+        var collection = new ArrayList { "apple", "banana" };
+        IEqualityComparer comparer = null!;
+
+        // Act
+        Action action = () => Assert.DoesNotContain("cherry", collection, comparer);
+
+        // Assert
+        action.Should().Throw<AssertFailedException>().WithMessage("Assert.DoesNotContain failed. The parameter 'comparer' is invalid. The value cannot be null.");
+    }
+
+    /// <summary>
+    /// Tests the DoesNotContain method (non-generic) with predicate when collection is null.
+    /// Expects an ArgumentNullException.
+    /// </summary>
+    public void DoesNotContain_InNonGenericCollection_Predicate_NullCollection_ThrowsException()
+    {
+        // Arrange
+        IEnumerable collection = null!;
+
+        // Act
+        Action action = () => Assert.DoesNotContain(Predicate, collection);
+
+        // Assert
+        action.Should().Throw<AssertFailedException>().WithMessage("Assert.DoesNotContain failed. The parameter 'collection' is invalid. The value cannot be null.");
+
+        // Local functions
+        static bool Predicate(object? x) => x is int i && i > 5;
+    }
+
+    /// <summary>
+    /// Tests the DoesNotContain method (non-generic) with null predicate.
+    /// Expects an ArgumentNullException.
+    /// </summary>
+    public void DoesNotContain_InNonGenericCollection_NullPredicate_ThrowsException()
+    {
+        // Arrange
+        var collection = new ArrayList { 1, 2, 3 };
+        Func<object?, bool> predicate = null!;
+
+        // Act
+        Action action = () => Assert.DoesNotContain(predicate, collection);
+
+        // Assert
+        action.Should().Throw<AssertFailedException>().WithMessage("Assert.DoesNotContain failed. The parameter 'predicate' is invalid. The value cannot be null.");
+    }
+
+    /// <summary>
+    /// Tests the string DoesNotContain method when substring is null.
+    /// Expects an ArgumentNullException.
+    /// </summary>
+    public void DoesNotContain_String_NullSubstring_ThrowsException()
+    {
+        // Arrange
+        string substring = null!;
+        string value = "test value";
+
+        // Act
+        Action action = () => Assert.DoesNotContain(substring, value);
+
+        // Assert
+        action.Should().Throw<AssertFailedException>().WithMessage("Assert.DoesNotContain failed. The parameter 'substring' is invalid. The value cannot be null.");
+    }
+
+    /// <summary>
+    /// Tests the string DoesNotContain method when value is null.
+    /// Expects an ArgumentNullException.
+    /// </summary>
+    public void DoesNotContain_String_NullValue_ThrowsException()
+    {
+        // Arrange
+        string substring = "test";
+        string value = null!;
+
+        // Act
+        Action action = () => Assert.DoesNotContain(substring, value);
+
+        // Assert
+        action.Should().Throw<AssertFailedException>().WithMessage("Assert.DoesNotContain failed. The parameter 'value' is invalid. The value cannot be null.");
+    }
+
+    /// <summary>
+    /// Tests the string DoesNotContain method with StringComparison when substring is null.
+    /// Expects an ArgumentNullException.
+    /// </summary>
+    public void DoesNotContain_String_WithComparison_NullSubstring_ThrowsException()
+    {
+        // Arrange
+        string substring = null!;
+        string value = "test value";
+
+        // Act
+        Action action = () => Assert.DoesNotContain(substring, value, StringComparison.OrdinalIgnoreCase);
+
+        // Assert
+        action.Should().Throw<AssertFailedException>().WithMessage("Assert.DoesNotContain failed. The parameter 'substring' is invalid. The value cannot be null.");
+    }
+
+    /// <summary>
+    /// Tests the string DoesNotContain method with StringComparison when value is null.
+    /// Expects an ArgumentNullException.
+    /// </summary>
+    public void DoesNotContain_String_WithComparison_NullValue_ThrowsException()
+    {
+        // Arrange
+        string substring = "test";
+        string value = null!;
+
+        // Act
+        Action action = () => Assert.DoesNotContain(substring, value, StringComparison.OrdinalIgnoreCase);
+
+        // Assert
+        action.Should().Throw<AssertFailedException>().WithMessage("Assert.DoesNotContain failed. The parameter 'value' is invalid. The value cannot be null.");
     }
 
     private static bool IsEven(int x) => x % 2 == 0;
@@ -996,7 +1419,7 @@ public void ContainsSinglePredicate_InNonGenericCollection_NoMessage_OneItemMatc
         var collection = new ArrayList { 1, 2, 3, 4, 5, "a" };
 
         // Act
-        object result = Assert.ContainsSingle(x => x.Equals(3), collection);
+        object? result = Assert.ContainsSingle(x => x.Equals(3), collection);
 
         // Assert
         result.Should().Be(3);
@@ -1029,7 +1452,7 @@ public void ContainsSinglePredicate_InNonGenericCollection_WithMessage_OneItemMa
 
         // Act
 #pragma warning disable CA1865 // Use char overload - not netfx
-        object result = Assert.ContainsSingle(x => x is string s && s.StartsWith("b", StringComparison.Ordinal), collection, "Expected one item starting with 'b'");
+        object? result = Assert.ContainsSingle(x => x is string s && s.StartsWith("b", StringComparison.Ordinal), collection, "Expected one item starting with 'b'");
 #pragma warning restore CA1865 // Use char overload
 
         // Assert
@@ -1049,7 +1472,8 @@ public void ContainsSinglePredicate_NoItemMatches_ThrowsException()
         Action action = () => Assert.ContainsSingle(x => x % 2 == 0, collection);
 
         // Assert
-        action.Should().Throw<AssertFailedException>().WithMessage("*Expected exactly one item to match the predicate but found 0 item(s)*");
+        action.Should().Throw<AssertFailedException>()
+            .WithMessage("Assert.ContainsSingle failed. Expected exactly one item to match the predicate but found 0 item(s). 'predicate' expression: 'x => x % 2 == 0', 'collection' expression: 'collection'.");
     }
 
     /// <summary>
@@ -1065,7 +1489,8 @@ public void ContainsSinglePredicate_InNonGenericCollection_NoItemMatches_ThrowsE
         Action action = () => Assert.ContainsSingle(x => x is int i && i % 2 == 0, collection);
 
         // Assert
-        action.Should().Throw<AssertFailedException>().WithMessage("*Expected exactly one item to match the predicate but found 0 item(s)*");
+        action.Should().Throw<AssertFailedException>()
+            .WithMessage("Assert.ContainsSingle failed. Expected exactly one item to match the predicate but found 0 item(s). 'predicate' expression: 'x => x is int i && i % 2 == 0', 'collection' expression: 'collection'.");
     }
 
     /// <summary>
@@ -1081,7 +1506,8 @@ public void ContainsSinglePredicate_MultipleItemsMatch_ThrowsException()
         Action action = () => Assert.ContainsSingle(x => x % 2 == 0, collection);
 
         // Assert
-        action.Should().Throw<AssertFailedException>().WithMessage("*Expected exactly one item to match the predicate but found 4 item(s)*");
+        action.Should().Throw<AssertFailedException>()
+            .WithMessage("Assert.ContainsSingle failed. Expected exactly one item to match the predicate but found 4 item(s). 'predicate' expression: 'x => x % 2 == 0', 'collection' expression: 'collection'.");
     }
 
     /// <summary>
@@ -1091,13 +1517,14 @@ public void ContainsSinglePredicate_MultipleItemsMatch_ThrowsException()
     public void ContainsSinglePredicate_InNonGenericCollection_MultipleItemsMatch_ThrowsException()
     {
         // Arrange
-        var collection = new ArrayList { 2, 4, 6, 8, "a" };
+        var collection = new ArrayList { 2, 4, "a" };
 
         // Act
         Action action = () => Assert.ContainsSingle(x => x is int i && i % 2 == 0, collection);
 
         // Assert
-        action.Should().Throw<AssertFailedException>().WithMessage("*Expected exactly one item to match the predicate but found * item(s)*");
+        action.Should().Throw<AssertFailedException>()
+            .WithMessage("Assert.ContainsSingle failed. Expected exactly one item to match the predicate but found 2 item(s). 'predicate' expression: 'x => x is int i && i % 2 == 0', 'collection' expression: 'collection'.");
     }
 
     /// <summary>
@@ -1113,7 +1540,8 @@ public void ContainsSinglePredicate_WithMessage_NoItemMatches_ThrowsException()
         Action action = () => Assert.ContainsSingle(x => x % 2 == 0, collection, $"No even numbers found in collection with {collection.Count} items");
 
         // Assert
-        action.Should().Throw<AssertFailedException>().WithMessage("*No even numbers found in collection with 3 items*");
+        action.Should().Throw<AssertFailedException>()
+            .WithMessage("Assert.ContainsSingle failed. Expected exactly one item to match the predicate but found 0 item(s). 'predicate' expression: 'x => x % 2 == 0', 'collection' expression: 'collection'. No even numbers found in collection with 3 items");
     }
 
     /// <summary>
@@ -1129,7 +1557,8 @@ public void ContainsSinglePredicate_InNonGenericCollection_WithMessage_NoItemMat
         Action action = () => Assert.ContainsSingle(x => x is int i && i % 2 == 0, collection, $"No even numbers found in collection with {collection.Count} items");
 
         // Assert
-        action.Should().Throw<AssertFailedException>().WithMessage("*No even numbers found in collection with 3 items*");
+        action.Should().Throw<AssertFailedException>()
+            .WithMessage("Assert.ContainsSingle failed. Expected exactly one item to match the predicate but found 0 item(s). 'predicate' expression: 'x => x is int i && i % 2 == 0', 'collection' expression: 'collection'. No even numbers found in collection with 3 items");
     }
 
     /// <summary>
@@ -1145,7 +1574,8 @@ public void ContainsSinglePredicate_WithMessage_MultipleItemsMatch_ThrowsExcepti
         Action action = () => Assert.ContainsSingle(x => x % 2 == 0, collection, $"Too many even numbers found: {collection.Count}");
 
         // Assert
-        action.Should().Throw<AssertFailedException>().WithMessage("*Too many even numbers found: 3*");
+        action.Should().Throw<AssertFailedException>()
+            .WithMessage("Assert.ContainsSingle failed. Expected exactly one item to match the predicate but found 3 item(s). 'predicate' expression: 'x => x % 2 == 0', 'collection' expression: 'collection'. Too many even numbers found: 3");
     }
 
     /// <summary>
@@ -1155,13 +1585,14 @@ public void ContainsSinglePredicate_WithMessage_MultipleItemsMatch_ThrowsExcepti
     public void ContainsSinglePredicate_InNonGenericCollection_WithMessage_MultipleItemsMatch_ThrowsException()
     {
         // Arrange
-        var collection = new ArrayList { 2, 4, 6 };
+        var collection = new ArrayList { 2, 4, "a" };
 
         // Act
-        Action action = () => Assert.ContainsSingle(x => x is int i && i % 2 == 0, collection, $"Too many even numbers found: {collection.Count}");
+        Action action = () => Assert.ContainsSingle(x => x is int i && i % 2 == 0, collection, "Too many even numbers found: 2");
 
         // Assert
-        action.Should().Throw<AssertFailedException>().WithMessage("*Too many even numbers found: 3*");
+        action.Should().Throw<AssertFailedException>()
+            .WithMessage("Assert.ContainsSingle failed. Expected exactly one item to match the predicate but found 2 item(s). 'predicate' expression: 'x => x is int i && i % 2 == 0', 'collection' expression: 'collection'. Too many even numbers found: 2");
     }
 
     /// <summary>
@@ -1199,9 +1630,10 @@ public void ContainsSinglePredicate_InNonGenericCollection_ComplexObjects_OneIte
         };
 
         // Act
-        object result = Assert.ContainsSingle(p => p is Person person && person.Age == 30, items);
+        object? result = Assert.ContainsSingle(p => p is Person person && person.Age == 30, items);
 
         // Assert
+        result.Should().BeOfType<Person>();
         var resultPerson = (Person)result;
         resultPerson.Name.Should().Be("Bob");
         resultPerson.Age.Should().Be(30);
@@ -1231,7 +1663,7 @@ public void ContainsSinglePredicate_InNonGenericCollection_WithNullValues_OneIte
         var collection = new ArrayList { "apple", null, "banana" };
 
         // Act
-        object result = Assert.ContainsSingle(x => x == null, collection);
+        object? result = Assert.ContainsSingle(x => x == null, collection);
 
         // Assert
         result.Should().BeNull();
@@ -1251,7 +1683,8 @@ public void Contains_ItemNotFound_ShowsSpecificErrorMessage()
         Action action = () => Assert.Contains(5, collection);
 
         // Assert
-        action.Should().Throw<AssertFailedException>().WithMessage("*Expected collection to contain the specified item*");
+        action.Should().Throw<AssertFailedException>()
+            .WithMessage("Assert.Contains failed. Expected collection to contain the specified item. 'expected' expression: '5', 'collection' expression: 'collection'.");
     }
 
     /// <summary>
@@ -1266,7 +1699,8 @@ public void Contains_InNonGenericCollection_ItemNotFound_ShowsSpecificErrorMessa
         Action action = () => Assert.Contains(5, collection);
 
         // Assert
-        action.Should().Throw<AssertFailedException>().WithMessage("*Expected collection to contain the specified item*");
+        action.Should().Throw<AssertFailedException>()
+            .WithMessage("Assert.Contains failed. Expected collection to contain the specified item. 'expected' expression: '5', 'collection' expression: 'collection'.");
     }
 
     /// <summary>
@@ -1281,7 +1715,8 @@ public void Contains_PredicateNotMatched_ShowsSpecificErrorMessage()
         Action action = () => Assert.Contains(x => x % 2 == 0, collection);
 
         // Assert
-        action.Should().Throw<AssertFailedException>().WithMessage("*Expected at least one item to match the predicate*");
+        action.Should().Throw<AssertFailedException>()
+            .WithMessage("Assert.Contains failed. Expected at least one item to match the predicate. 'predicate' expression: 'x => x % 2 == 0', 'collection' expression: 'collection'.");
     }
 
     /// <summary>
@@ -1296,7 +1731,8 @@ public void DoesNotContain_ItemFound_ShowsSpecificErrorMessage()
         Action action = () => Assert.DoesNotContain(2, collection);
 
         // Assert
-        action.Should().Throw<AssertFailedException>().WithMessage("*Expected collection to not contain the specified item*");
+        action.Should().Throw<AssertFailedException>()
+            .WithMessage("Assert.DoesNotContain failed. Expected collection to not contain the specified item. 'notExpected' expression: '2', 'collection' expression: 'collection'.");
     }
 
     /// <summary>
@@ -1311,7 +1747,8 @@ public void DoesNotContain_PredicateMatched_ShowsSpecificErrorMessage()
         Action action = () => Assert.DoesNotContain(x => x % 2 == 0, collection);
 
         // Assert
-        action.Should().Throw<AssertFailedException>().WithMessage("*Expected no items to match the predicate*");
+        action.Should().Throw<AssertFailedException>()
+            .WithMessage("Assert.DoesNotContain failed. Expected no items to match the predicate. 'predicate' expression: 'x => x % 2 == 0', 'collection' expression: 'collection'.");
     }
 
     public void DoesNotContains_HashSetWithCustomComparer_ItemDoesNotExist_DoesNotThrow()