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Include full exception (stack trace + inner exceptions) in Assert.Throws* failure messages #9212

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Merged
Evangelink merged 2 commits into from
Jun 17, 2026
Merged

Include full exception (stack trace + inner exceptions) in Assert.Throws* failure messages #9212

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88d42dc
Include full exception (stack trace + inner exceptions) in Assert.Thr…
Evangelink Jun 17, 2026
6f4e2b0
Address review: preserve friendly generic type name in 'actual except…
Evangelink Jun 17, 2026
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9 changes: 6 additions & 3 deletions docs/RFCs/012-Structured-Assertion-Messages.md
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Original file line number Diff line number Diff line change
Expand Up @@ -307,8 +307,9 @@ Assert.ThrowsExactly<ArgumentException>(() => Validate(input))
Assertion failed. Expected exception of exact type ArgumentException but caught InvalidOperationException.

expected type: System.ArgumentException
actual type: System.InvalidOperationException
actual exception: System.InvalidOperationException: Operation is not valid due to the current state of the object.
at MyApp.Service.Validate(String input) in Service.cs:line 42
at MyTests.ValidationTests.InvalidInput_ShouldThrow() in ValidationTests.cs:line 18

Assert.ThrowsExactly<ArgumentException>(() => Validate(input))
at MyTests.ValidationTests.InvalidInput_ShouldThrow() in ValidationTests.cs:line 18
Expand Down Expand Up @@ -679,8 +680,9 @@ Assertion failed. Expected exception of type ArgumentException (or derived) but
Assertion failed. Expected exception of type ArgumentException (or derived) but caught InvalidOperationException.

expected type: System.ArgumentException (or derived)
actual type: System.InvalidOperationException
actual exception: System.InvalidOperationException: Operation is not valid due to the current state of the object.
at MyApp.Service.Validate(String input) in Service.cs:line 42
at MyTests.ValidationTests.InvalidInput_ShouldThrow() in ValidationTests.cs:line 18
```

#### Assert.ThrowsExactly (no exception thrown)
Expand All @@ -695,8 +697,9 @@ Assertion failed. Expected exception of exact type ArgumentException but no exce
Assertion failed. Expected exception of exact type ArgumentException but caught ArgumentNullException.

expected type: System.ArgumentException
actual type: System.ArgumentNullException
actual exception: System.ArgumentNullException: Value cannot be null.
at MyApp.Service.Validate(String input) in Service.cs:line 42
at MyTests.ValidationTests.InvalidInput_ShouldThrow() in ValidationTests.cs:line 18
```

#### Assert.ThrowsAsync / Assert.ThrowsExactlyAsync
Expand Down
17 changes: 13 additions & 4 deletions src/TestFramework/TestFramework/Assertions/Assert.ThrowsException.Core.cs
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Expand Up @@ -172,19 +172,28 @@ private static void ReportThrowsFailed<TException>(
Exception actualException = state.ExceptionThrown!;
Type actualType = actualException.GetType();
string actualTypeName = GetDisplayTypeName(actualType, includeNamespace: false);
string actualTypeFullName = GetDisplayTypeName(actualType, includeNamespace: true);

string summary = isStrictType
? $"Expected exception of exact type {expectedTypeName} but caught {actualTypeName}."
: $"Expected exception of type {expectedTypeName} (or derived) but caught {actualTypeName}.";

string expectedTypeLabel = isStrictType ? expectedTypeFullName : $"{expectedTypeFullName} (or derived)";

// The "actual exception:" line is already prefixed with the exception type name, so we don't emit a
// separate "actual type:" line to avoid duplicating that information.
// Render the full exception (type, message, inner-exception chain and stack trace) via ToString so the
// unexpected exception can be diagnosed without re-running under a debugger. See issue #9190.
// Exception.ToString() prefixes the output with Type.ToString(), which uses CLR notation for generic
// types (e.g. "MyException`1[System.Int32]"). Replace that leading prefix with the friendly name so it
// stays consistent with the "expected type:" line; for non-generic types the two notations are identical.
string actualExceptionText = actualException.ToString();
string clrTypeName = actualType.ToString();
if (actualExceptionText.StartsWith(clrTypeName, StringComparison.Ordinal))
{
actualExceptionText = GetDisplayTypeName(actualType, includeNamespace: true) + actualExceptionText.Substring(clrTypeName.Length);
}

EvidenceBlock evidence = EvidenceBlock.Create()
.AddLine("expected type:", expectedTypeLabel)
.AddLine("actual exception:", $"{actualTypeFullName}: {actualException.Message}");
.AddLine("actual exception:", actualExceptionText);

message = new StructuredAssertionMessage(summary)
.WithUserMessage(userMessage)
Expand Down
76 changes: 18 additions & 58 deletions test/UnitTests/TestFramework.UnitTests/Assertions/AssertTests.ThrowsExceptionTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -70,12 +70,12 @@ public void ThrowsAsync_WhenExceptionIsNotExpectedType_ShouldThrow()
Action action = t.Wait;
action.Should().Throw<AggregateException>()
.WithInnerException<AssertFailedException>()
.Which.Message.Should().Be(
.Which.Message.Should().Match(
"""
Assertion failed. Expected exception of type ArgumentException (or derived) but caught Exception.

expected type: System.ArgumentException (or derived)
actual exception: System.Exception: Exception of type 'System.Exception' was thrown.
actual exception: System.Exception: Exception of type 'System.Exception' was thrown.*

Assert.ThrowsAsync<ArgumentException>(() => throw new Exception())
""");
Expand All @@ -87,12 +87,12 @@ public void ThrowsExactlyAsync_WhenExceptionIsDerivedFromExpectedType_ShouldThro
Action action = t.Wait;
action.Should().Throw<AggregateException>()
.WithInnerException<AssertFailedException>()
.Which.Message.Should().Be(
.Which.Message.Should().Match(
"""
Assertion failed. Expected exception of exact type ArgumentException but caught ArgumentNullException.

expected type: System.ArgumentException
actual exception: System.ArgumentNullException: Value cannot be null.
actual exception: System.ArgumentNullException: Value cannot be null.*

Assert.ThrowsExactlyAsync<ArgumentException>(() => throw new ArgumentNullException())
""");
Expand Down Expand Up @@ -144,23 +144,13 @@ public void Throws_WithMessageBuilder_FailsBecauseTypeMismatch()
return "message constructed via builder.";
});
action.Should().Throw<AssertFailedException>()
.Which.Message.Should().BeOneOf(
"""
Assertion failed. Expected exception of type ArgumentNullException (or derived) but caught ArgumentOutOfRangeException.
message constructed via builder.

expected type: System.ArgumentNullException (or derived)
actual exception: System.ArgumentOutOfRangeException: Specified argument was out of the range of valid values. (Parameter 'MyParamNameHere')

Assert.Throws<ArgumentNullException>(() => throw new ArgumentOutOfRangeException("MyParamNameHere"))
""",
.Which.Message.Should().Match(
"""
Assertion failed. Expected exception of type ArgumentNullException (or derived) but caught ArgumentOutOfRangeException.
message constructed via builder.

expected type: System.ArgumentNullException (or derived)
actual exception: System.ArgumentOutOfRangeException: Specified argument was out of the range of valid values.
Parameter name: MyParamNameHere
actual exception: System.ArgumentOutOfRangeException: Specified argument was out of the range of valid values.*MyParamNameHere*

Assert.Throws<ArgumentNullException>(() => throw new ArgumentOutOfRangeException("MyParamNameHere"))
""");
Expand Down Expand Up @@ -216,23 +206,13 @@ public void ThrowsExactly_WithMessageBuilder_FailsBecauseTypeMismatch()
return "message constructed via builder.";
});
action.Should().Throw<AssertFailedException>()
.Which.Message.Should().BeOneOf(
.Which.Message.Should().Match(
"""
Assertion failed. Expected exception of exact type ArgumentNullException but caught ArgumentOutOfRangeException.
message constructed via builder.

expected type: System.ArgumentNullException
actual exception: System.ArgumentOutOfRangeException: Specified argument was out of the range of valid values. (Parameter 'MyParamNameHere')

Assert.ThrowsExactly<ArgumentNullException>(() => throw new ArgumentOutOfRangeException("MyParamNameHere"))
""",
"""
Assertion failed. Expected exception of exact type ArgumentNullException but caught ArgumentOutOfRangeException.
message constructed via builder.

expected type: System.ArgumentNullException
actual exception: System.ArgumentOutOfRangeException: Specified argument was out of the range of valid values.
Parameter name: MyParamNameHere
actual exception: System.ArgumentOutOfRangeException: Specified argument was out of the range of valid values.*MyParamNameHere*

Assert.ThrowsExactly<ArgumentNullException>(() => throw new ArgumentOutOfRangeException("MyParamNameHere"))
""");
Expand Down Expand Up @@ -288,23 +268,13 @@ public async Task ThrowsAsync_WithMessageBuilder_FailsBecauseTypeMismatch()
return "message constructed via builder.";
});
(await action.Should().ThrowAsync<AssertFailedException>())
.Which.Message.Should().BeOneOf(
.Which.Message.Should().Match(
"""
Assertion failed. Expected exception of type ArgumentNullException (or derived) but caught ArgumentOutOfRangeException.
message constructed via builder.

expected type: System.ArgumentNullException (or derived)
actual exception: System.ArgumentOutOfRangeException: Specified argument was out of the range of valid values. (Parameter 'MyParamNameHere')

Assert.ThrowsAsync<ArgumentNullException>(() => Task.FromException(new ArgumentOutOfRangeException("MyParamNameHere")))
""",
"""
Assertion failed. Expected exception of type ArgumentNullException (or derived) but caught ArgumentOutOfRangeException.
message constructed via builder.

expected type: System.ArgumentNullException (or derived)
actual exception: System.ArgumentOutOfRangeException: Specified argument was out of the range of valid values.
Parameter name: MyParamNameHere
actual exception: System.ArgumentOutOfRangeException: Specified argument was out of the range of valid values.*MyParamNameHere*

Assert.ThrowsAsync<ArgumentNullException>(() => Task.FromException(new ArgumentOutOfRangeException("MyParamNameHere")))
""");
Expand Down Expand Up @@ -360,23 +330,13 @@ public async Task ThrowsExactlyAsync_WithMessageBuilder_FailsBecauseTypeMismatch
return "message constructed via builder.";
});
(await action.Should().ThrowAsync<AssertFailedException>())
.Which.Message.Should().BeOneOf(
"""
Assertion failed. Expected exception of exact type ArgumentNullException but caught ArgumentOutOfRangeException.
message constructed via builder.

expected type: System.ArgumentNullException
actual exception: System.ArgumentOutOfRangeException: Specified argument was out of the range of valid values. (Parameter 'MyParamNameHere')

Assert.ThrowsExactlyAsync<ArgumentNullException>(() => Task.FromException(new ArgumentOutOfRangeException("MyParamNameHere")))
""",
.Which.Message.Should().Match(
"""
Assertion failed. Expected exception of exact type ArgumentNullException but caught ArgumentOutOfRangeException.
message constructed via builder.

expected type: System.ArgumentNullException
actual exception: System.ArgumentOutOfRangeException: Specified argument was out of the range of valid values.
Parameter name: MyParamNameHere
actual exception: System.ArgumentOutOfRangeException: Specified argument was out of the range of valid values.*MyParamNameHere*

Assert.ThrowsExactlyAsync<ArgumentNullException>(() => Task.FromException(new ArgumentOutOfRangeException("MyParamNameHere")))
""");
Expand Down Expand Up @@ -421,13 +381,13 @@ public void Throws_WhenExceptionMessageContainsNewline_ContinuationLinesAreInden

// "actual exception:" is the longest label (17 chars) + 1 space = 18 chars indent for the continuation line.
action.Should().Throw<AssertFailedException>()
.Which.Message.Should().Be(
.Which.Message.Should().Match(
"""
Assertion failed. Expected exception of type ArgumentException (or derived) but caught InvalidOperationException.

expected type: System.ArgumentException (or derived)
actual exception: System.InvalidOperationException: line1
line2
line2*

Assert.Throws<ArgumentException>(() => throw new InvalidOperationException("line1\nline2"))
""");
Expand All @@ -445,12 +405,12 @@ static void Action() => Assert.Throws<ArgumentException>(() =>
Action action = Action;

action.Should().Throw<AssertFailedException>()
.Which.Message.Should().Be(
.Which.Message.Should().Match(
"""
Assertion failed. Expected exception of type ArgumentException (or derived) but caught InvalidOperationException.

expected type: System.ArgumentException (or derived)
actual exception: System.InvalidOperationException: oops
actual exception: System.InvalidOperationException: oops*

Assert.Throws<ArgumentException>(<action>)
""");
Expand All @@ -464,12 +424,12 @@ public void Throws_WhenExpectedTypeIsGeneric_RendersFriendlyTypeName()
Action action = Action;

action.Should().Throw<AssertFailedException>()
.Which.Message.Should().Be(
.Which.Message.Should().Match(
"""
Assertion failed. Expected exception of type ThrowsTestGenericException<Int32> (or derived) but caught InvalidOperationException.

expected type: Microsoft.VisualStudio.TestPlatform.TestFramework.UnitTests.ThrowsTestGenericException<System.Int32> (or derived)
actual exception: System.InvalidOperationException: oops
actual exception: System.InvalidOperationException: oops*

Assert.Throws<ThrowsTestGenericException<Int32>>(() => throw new InvalidOperationException("oops"))
""");
Expand Down
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