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Oct 14, 2025
Merged

Fix overload resolution for IsTypeOf<> and nullable types #3365

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456e3f5
Fix overload resolution for IsTypeOf<> and nullable types
thomhurst Oct 14, 2025
59c3e79
Add unboxed value type tests for IsTypeOf<> method
thomhurst Oct 14, 2025
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285 changes: 285 additions & 0 deletions TUnit.Assertions.Tests/TypeOfTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,13 @@ namespace TUnit.Assertions.Tests;

public class TypeOfTests
{
// Test struct for custom struct testing
private struct CustomStruct
{
public int Value { get; init; }
public string Name { get; init; }
}

[Test]
public async Task Returns_Casted_Object()
{
Expand All @@ -13,4 +20,282 @@ public async Task Returns_Casted_Object()

await Assert.That(result).IsNotNull();
}

// ============ STRUCT / VALUE TYPE TESTS ============

[Test]
public async Task IsTypeOf_BoxedInt_Success()
{
object boxedInt = 42;

var result = await Assert.That(boxedInt).IsTypeOf<int>();

await Assert.That(result).IsEqualTo(42);
}

[Test]
public async Task IsTypeOf_BoxedDateTime_Success()
{
var expectedDate = new DateTime(2025, 10, 14);
object boxedDateTime = expectedDate;

var result = await Assert.That(boxedDateTime).IsTypeOf<DateTime>();

await Assert.That(result).IsEqualTo(expectedDate);
}

[Test]
public async Task IsTypeOf_BoxedGuid_Success()
{
var expectedGuid = Guid.NewGuid();
object boxedGuid = expectedGuid;

var result = await Assert.That(boxedGuid).IsTypeOf<Guid>();

await Assert.That(result).IsEqualTo(expectedGuid);
}

[Test]
public async Task IsTypeOf_CustomStruct_Success()
{
var customStruct = new CustomStruct { Value = 10, Name = "Test" };
object boxedCustom = customStruct;

var result = await Assert.That(boxedCustom).IsTypeOf<CustomStruct>();

await Assert.That(result.Value).IsEqualTo(10);
await Assert.That(result.Name).IsEqualTo("Test");
}

[Test]
public async Task IsTypeOf_NullableInt_WithTwoTypeParameters_Success()
{
int? nullableInt = 42;

var result = await Assert.That(nullableInt).IsTypeOf<int?, int?>();

await Assert.That(result).IsEqualTo(42);
}

[Test]
public async Task IsTypeOf_BoxedNullableInt_Success()
{
object? boxedNullableInt = (int?)42;

var result = await Assert.That(boxedNullableInt).IsTypeOf<int?>();

await Assert.That(result).IsEqualTo(42);
}

[Test]
public async Task IsTypeOf_StructTypeMismatch_Fails()
{
object boxedInt = 42;

await Assert.ThrowsAsync<TUnit.Assertions.Exceptions.AssertionException>(async () =>
{
await Assert.That(boxedInt).IsTypeOf<long>();
});
}

[Test]
public async Task IsTypeOf_DecimalStruct_Success()
{
object boxedDecimal = 123.45m;

var result = await Assert.That(boxedDecimal).IsTypeOf<decimal>();

await Assert.That(result).IsEqualTo(123.45m);
}

[Test]
public async Task IsTypeOf_TimeSpanStruct_Success()
{
var expectedTimeSpan = TimeSpan.FromHours(2);
object boxedTimeSpan = expectedTimeSpan;

var result = await Assert.That(boxedTimeSpan).IsTypeOf<TimeSpan>();

await Assert.That(result).IsEqualTo(expectedTimeSpan);
}

// ============ UNBOXED VALUE TYPE TESTS ============

[Test]
public async Task IsTypeOf_UnboxedInt_Success()
{
int number = 42;

// Using two type parameters - should work with unboxed value types
var result = await Assert.That(number).IsTypeOf<int, int>();

await Assert.That(result).IsEqualTo(42);
}

[Test]
public async Task IsTypeOf_UnboxedDateTime_Success()
{
var date = new DateTime(2025, 10, 14, 12, 30, 0);

var result = await Assert.That(date).IsTypeOf<DateTime, DateTime>();

await Assert.That(result).IsEqualTo(date);
}

[Test]
public async Task IsTypeOf_UnboxedGuid_Success()
{
var guid = Guid.NewGuid();

var result = await Assert.That(guid).IsTypeOf<Guid, Guid>();

await Assert.That(result).IsEqualTo(guid);
}

[Test]
public async Task IsTypeOf_UnboxedBool_Success()
{
bool value = true;

var result = await Assert.That(value).IsTypeOf<bool, bool>();

await Assert.That(result).IsTrue();
}

[Test]
public async Task IsTypeOf_UnboxedDouble_Success()
{
double value = 3.14159;

var result = await Assert.That(value).IsTypeOf<double, double>();

await Assert.That(result).IsEqualTo(3.14159);
}

[Test]
public async Task IsTypeOf_UnboxedCustomStruct_Success()
{
var customStruct = new CustomStruct { Value = 99, Name = "Unboxed" };

var result = await Assert.That(customStruct).IsTypeOf<CustomStruct, CustomStruct>();

await Assert.That(result.Value).IsEqualTo(99);
await Assert.That(result.Name).IsEqualTo("Unboxed");
}

// ============ NULLABLE COLLECTION TESTS ============

[Test]
public async Task IsNotNull_NullableByteArray_ReturnsNonNull()
{
byte[]? nullableBytes = new byte[] { 1, 2, 3 };

// IsNotNull should succeed and return non-null collection
var result = await Assert.That(nullableBytes).IsNotNull();

// Result should be enumerable with 3 elements
await Assert.That(result.Count()).IsEqualTo(3);
await Assert.That(result.First()).IsEqualTo((byte)1);
}

[Test]
public async Task IsNotNull_NullableIntArray_ReturnsNonNull()
{
int[]? nullableArray = new int[] { 10, 20, 30 };

// IsNotNull should succeed and return non-null collection
var result = await Assert.That(nullableArray).IsNotNull();

await Assert.That(result.Count()).IsEqualTo(3);
await Assert.That(result.ElementAt(1)).IsEqualTo(20);
}

[Test]
public async Task IsNotNull_NullableList_ReturnsNonNull()
{
List<string>? nullableList = new List<string> { "a", "b", "c" };

// IsNotNull should succeed and return non-null collection
var result = await Assert.That(nullableList).IsNotNull();

// Result should be enumerable with 3 elements
await Assert.That(result.Count()).IsEqualTo(3);
await Assert.That(result.First()).IsEqualTo("a");
}

[Test]
public async Task IsNotNull_NullableIEnumerable_ReturnsIEnumerable()
{
IEnumerable<int>? nullableEnumerable = Enumerable.Range(1, 5);

var result = await Assert.That(nullableEnumerable).IsNotNull();

// Result should be enumerable
await Assert.That(result.Count()).IsEqualTo(5);
await Assert.That(result.First()).IsEqualTo(1);
}

[Test]
public async Task CollectionAssertion_NullableByteArray_CanUseCollectionMethods()
{
byte[]? nullableBytes = new byte[] { 1, 2, 3, 4, 5 };

// Should be able to use collection assertion methods
await Assert.That(nullableBytes).HasCount(5);
await Assert.That(nullableBytes).Contains((byte)3);
await Assert.That(nullableBytes).IsInOrder();
}

[Test]
public async Task CollectionAssertion_NullableList_CanUseCollectionMethods()
{
List<int>? nullableList = new List<int> { 10, 20, 30 };

await Assert.That(nullableList).HasCount(3);
await Assert.That(nullableList).Contains(20);
await Assert.That(nullableList).IsInOrder();
}

[Test]
public async Task CollectionAssertion_NullableIEnumerable_CanUseCollectionMethods()
{
IEnumerable<string>? nullableEnumerable = new[] { "apple", "banana", "cherry" };

await Assert.That(nullableEnumerable).HasCount(3);
await Assert.That(nullableEnumerable).Contains("banana");
await Assert.That(nullableEnumerable).IsInOrder();
}

// ============ REFERENCE TYPE TESTS (existing behavior verification) ============

[Test]
public async Task IsTypeOf_String_Success()
{
object obj = "Hello";

var result = await Assert.That(obj).IsTypeOf<string>();

await Assert.That(result).IsEqualTo("Hello");
}

[Test]
public async Task IsTypeOf_StringBuilder_Success()
{
object obj = new StringBuilder("Test");

var result = await Assert.That(obj).IsTypeOf<StringBuilder>();

await Assert.That(result.ToString()).IsEqualTo("Test");
}

[Test]
public async Task IsTypeOf_ReferenceTypeMismatch_Fails()
{
object obj = "Hello";

await Assert.ThrowsAsync<TUnit.Assertions.Exceptions.AssertionException>(async () =>
{
await Assert.That(obj).IsTypeOf<StringBuilder>();
});
}
}
18 changes: 9 additions & 9 deletions TUnit.Assertions/Extensions/Assert.cs
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Expand Up @@ -63,39 +63,39 @@ public static DictionaryAssertion<TKey, TValue> That<TKey, TValue>(
}

/// <summary>
/// Creates an assertion for an array.
/// Creates an assertion for an array (nullable or non-nullable).
/// This overload enables better type inference for collection operations like IsInOrder, All, ContainsOnly.
/// Example: await Assert.That(array).IsInOrder();
/// </summary>
public static CollectionAssertion<TItem> That<TItem>(
TItem[] value,
TItem[]? value,
[CallerArgumentExpression(nameof(value))] string? expression = null)
{
return new CollectionAssertion<TItem>(value, expression);
return new CollectionAssertion<TItem>(value!, expression);
}

/// <summary>
/// Creates an assertion for a List.
/// Creates an assertion for a List (nullable or non-nullable).
/// This overload enables better type inference for collection operations like IsInOrder, All, ContainsOnly.
/// Example: await Assert.That(list).IsInOrder();
/// </summary>
public static CollectionAssertion<TItem> That<TItem>(
List<TItem> value,
List<TItem>? value,
[CallerArgumentExpression(nameof(value))] string? expression = null)
{
return new CollectionAssertion<TItem>(value, expression);
return new CollectionAssertion<TItem>(value!, expression);
}

/// <summary>
/// Creates an assertion for an IEnumerable.
/// Creates an assertion for an IEnumerable (nullable or non-nullable).
/// This overload enables better type inference for collection operations like IsInOrder, All, ContainsOnly.
/// Example: await Assert.That(enumerable).IsInOrder();
/// </summary>
public static CollectionAssertion<TItem> That<TItem>(
IEnumerable<TItem> value,
IEnumerable<TItem>? value,
[CallerArgumentExpression(nameof(value))] string? expression = null)
{
return new CollectionAssertion<TItem>(value, expression);
return new CollectionAssertion<TItem>(value!, expression);
}

/// <summary>
Expand Down
19 changes: 10 additions & 9 deletions TUnit.Assertions/Extensions/AssertionExtensions.cs
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Expand Up @@ -357,25 +357,26 @@ public static Chaining.OrAssertion<TValue> IsNotEqualTo<TValue>(
// IsTypeOf(Type), IsAssignableTo, IsNotAssignableTo are now generated by AssertionExtensionGenerator

/// <summary>
/// Asserts that the value is of the specified type and returns an assertion on the casted value (specialized for object).
/// Asserts that the value is of the specified type and returns an assertion on the casted value.
/// Example: await Assert.That(obj).IsTypeOf<StringBuilder>();
/// This generic overload works with any source type.
/// </summary>
public static TypeOfAssertion<object, TExpected> IsTypeOf<TExpected>(
this IAssertionSource<object> source)
public static TypeOfAssertion<TValue, TExpected> IsTypeOf<TExpected, TValue>(
this IAssertionSource<TValue> source)
{
source.Context.ExpressionBuilder.Append($".IsTypeOf<{typeof(TExpected).Name}>()");
return new TypeOfAssertion<object, TExpected>(source.Context);
return new TypeOfAssertion<TValue, TExpected>(source.Context);
}

/// <summary>
/// Asserts that the value is of the specified type and returns an assertion on the casted value.
/// Asserts that the value is of the specified type and returns an assertion on the casted value (specialized for object).
/// Example: await Assert.That(obj).IsTypeOf<StringBuilder>();
/// </summary>
public static TypeOfAssertion<TFrom, TTo> IsTypeOf<TTo, TFrom>(
this IAssertionSource<TFrom> source)
public static TypeOfAssertion<object, TExpected> IsTypeOf<TExpected>(
this IAssertionSource<object> source)
{
source.Context.ExpressionBuilder.Append($".IsTypeOf<{typeof(TTo).Name}>()");
return new TypeOfAssertion<TFrom, TTo>(source.Context);
source.Context.ExpressionBuilder.Append($".IsTypeOf<{typeof(TExpected).Name}>()");
return new TypeOfAssertion<object, TExpected>(source.Context);
}

/// <summary>
Expand Down
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