fix: MockTimeProvider constructor treats "now" having DateTimeKind.Unspecified as if it had DateTimeKind.Local

Source/Testably.Abstractions.Testing/TimeProvider.cs

@@ -34,6 +34,9 @@ public static ITimeProvider Random()
 	/// <summary>
 	///     Initializes the <see cref="MockTimeSystem.TimeProvider" /> with the specified <paramref name="time" />.
 	/// </summary>
+	/// <remarks>
+	///     If the <paramref name="time" /> has Kind DateTimeKind.Unspecified it will be treated as if it had Kind DateTimeKind.Local.
+	/// </remarks>
 	public static ITimeProvider Use(DateTime time)
 	{
 		return new TimeProviderMock(time, "Fixed");

Source/Testably.Abstractions.Testing/TimeSystem/TimeProviderMock.cs

@@ -17,7 +17,10 @@ internal sealed class TimeProviderMock : ITimeProvider
 
 	public TimeProviderMock(DateTime now, string description)
 	{
-		_now = now;
+		_now = now.Kind == DateTimeKind.Unspecified
+			? DateTime.SpecifyKind(now, DateTimeKind.Local)
+			: now;
+
 		_description = description;
 	}
 

Tests/Testably.Abstractions.Testing.Tests/MockTimeSystemTests.cs

@@ -52,6 +52,22 @@ async Task Act()
 		await That(Act).ThrowsExactly<ArgumentOutOfRangeException>().WithParamName("delay");
 	}
 
+	[Theory]
+	[InlineData(DateTimeKind.Local)]
+	[InlineData(DateTimeKind.Unspecified)]
+	[InlineData(DateTimeKind.Utc)]
+	public async Task DifferenceBetweenDateTimeNowAndDateTimeUtcNow_ShouldBeLocalTimeZoneOffsetFromUtc(DateTimeKind dateTimeKind)
+	{
+		DateTime now = TimeTestHelper.GetRandomTime(DateTimeKind.Local);
+
+		var expectedDifference = TimeZoneInfo.Local.GetUtcOffset(now);
+
+		MockTimeSystem timeSystem = new(DateTime.SpecifyKind(now, dateTimeKind));
+		var actualDifference = timeSystem.DateTime.Now - timeSystem.DateTime.UtcNow;
+
+		await That(actualDifference).IsEqualTo(expectedDifference);
+	}
+
 	[Fact]
 	public async Task Sleep_Infinite_ShouldNotThrowException()
 	{

Tests/Testably.Abstractions.Testing.Tests/TimeProviderTests.cs

@@ -59,4 +59,13 @@ public async Task Use_ShouldReturnFixedDateTime()
 		await That(result1).IsEqualTo(now);
 		await That(result2).IsEqualTo(now);
 	}
+
+	[Fact]
+	public async Task Use_UnspecifiedKind_ShouldConvertToLocalDateTime()
+	{
+		DateTime unspecifiedTime = TimeTestHelper.GetRandomTime(DateTimeKind.Unspecified);
+		ITimeProvider timeProvider = TimeProvider.Use(unspecifiedTime);
+		DateTime result1 = timeProvider.Read();
+		await That(result1).IsEqualTo(DateTime.SpecifyKind(unspecifiedTime, DateTimeKind.Local));
+	}
 }