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

[Amaury Levé (Evangelink)]

Fixes#9190.

What

When Assert.Throws* / Assert.ThrowsExactly* (and their async variants) fail because the wrong exception type was caught, the failure message now renders the caught exception's full Exception.ToString() — type, message, inner-exception chain, and stack trace — on the actual exception: evidence line, instead of just {type}: {message}.

This lets you diagnose an unexpected exception (which inner exception, which line) directly from the failure message, without re-running under a debugger.

Before

Assertion failed. Expected exception of exact type NotSupportedException but caught InvalidOperationException.
expected type: System.NotSupportedException
actual exception: System.InvalidOperationException: C
Assert.ThrowsExactly<NotSupportedException>(Do)

After

Assertion failed. Expected exception of exact type NotSupportedException but caught InvalidOperationException.
expected type: System.NotSupportedException
actual exception: System.InvalidOperationException: C
---> System.ArgumentException: B
---> System.NullReferenceException: Object reference not set to an instance of an object.
at DogFood.ThrowTest.Do() in ThrowTest.cs:line 6
--- End of inner exception stack trace ---
...
at DogFood.ThrowTest.Do() in ThrowTest.cs:line 9
Assert.ThrowsExactly<NotSupportedException>(Do)

How

• Assert.ThrowsException.Core.cs: actual exception: now uses actualException.ToString(). The existing EvidenceBlock already re-indents multi-line values, so the trace renders cleanly under the label. (Builds on Remove redundant 'actual type:' line from Assert.Throws* failure message #9195, which removed the now-redundant actual type: line.)
• Tests: the wrong-type failure-message assertions move from exact .Be() / .BeOneOf() to wildcard .Match() — the deterministic prefix + call-site is anchored, * absorbs the environment-dependent stack trace. The ArgumentOutOfRangeException cross-runtime BeOneOf cases collapse to a single pattern. "No exception thrown" cases are unchanged.
• Updated the Assert.Throws* examples in docs/RFCs/012-Structured-Assertion-Messages.md (also syncing them with the actual type: removal from Remove redundant 'actual type:' line from Assert.Throws* failure message #9195).

Validation

.\build.cmd -test -projects test\UnitTests\TestFramework.UnitTests — all tests pass on net48, net8.0, net9.0, net8.0-windows; 0 warnings, 0 errors. Confirmed the rendered output against the issue's exact repro.

[Copilot]

⚠️ Not ready to approve

Several updated .Match patterns no longer assert that ArgumentOutOfRangeException includes the parameter name in the rendered “actual exception:” text, weakening test coverage for an important evidence detail.

Pull request overview

This PR updates MSTest’s Assert.Throws* / Assert.ThrowsExactly* failure messaging so that, when the wrong exception type is caught, the “actual exception:” evidence line renders Exception.ToString() (including inner exceptions + stack trace). It also adjusts unit tests and documentation examples to reflect the new multi-line output.

Changes:

• Update Assert.ThrowsException.Core to emit the full actualException.ToString() in the evidence block for wrong-type failures.
• Update TestFramework.UnitTests expectations to use wildcard matching (.Match) to tolerate environment-dependent stack traces.
• Refresh RFC documentation examples to remove the redundant actual type: line and show the new stack-trace-inclusive output.

File summaries

File	Description
src/TestFramework/TestFramework/Assertions/Assert.ThrowsException.Core.cs	Switches “actual exception:” evidence from {Type}: {Message} to Exception.ToString() for richer diagnostics.
test/UnitTests/TestFramework.UnitTests/Assertions/AssertTests.ThrowsExceptionTests.cs	Updates failure-message assertions to wildcard-match stack traces and other runtime-dependent formatting.
docs/RFCs/012-Structured-Assertion-Messages.md	Updates structured assertion message examples to reflect the new actual exception: rendering.

Copilot's findings

• Files reviewed: 3/3 changed files
• Comments generated: 4

Note

Your feedback helps us improve the quality of this feature.
Please use 👍 or 👎 to tell us whether this assessment is correct.

[Amaury Levé (Evangelink)]

Note

🤖 Automated review by GitHub Copilot. Posted via a maintainer's GitHub token, so it appears under their account — the account owner did not write or approve this content personally. Generated by the Expert Code Review workflow. To request a follow-up action, reply by tagging @copilot directly.

#	Dimension	Verdict
1	Algorithmic Correctness	🟡 1 NIT
13	Test Completeness & Coverage	🟠 1 MODERATE

✅ 20/22 dimensions clean.

• Correctness — Exception.ToString() uses CLR generic notation on the actual exception: label while expected type: uses the friendly <T> format (see inline comment)
• Test Completeness — the primary motivation of the PR (inner exception chain display) has no automated test

---

Dimension 13 — Test Completeness (MODERATE)

The PR description highlights the inner exception chain as the key diagnostic improvement (the ---> System.ArgumentException: B lines in the "After" example). The tests updated here only exercise the stack-trace suffix — they use * to absorb everything after the exception message, so they would pass even if inner exceptions were silently dropped.

A focused test would cover the new behaviour directly, e.g.:

publicvoidThrows_WhenExceptionHasInnerException_InnerExceptionChainIsRenderedInMessage(){varinner=newArgumentNullException("p");Actionaction=()=>Assert.ThrowsExactly<InvalidOperationException>(()=>thrownewArgumentException("outer",inner));action.Should().Throw<AssertFailedException>().Which.Message.Should().Contain(" ---> System.ArgumentNullException: ");}

This pins the ---> format and confirms the chain surfaces in the assertion failure message. Without it, a future change that truncates ToString() output (e.g., for size) would not be caught by the test suite.

---

Dimension 1 — Correctness NIT (see inline)

Addressed inline on Assert.ThrowsException.Core.cs line 186. For the common case (non-generic exception types) there is no observable difference. The regression only manifests when the caught exception type itself is generic, which is very rare in practice. Feel free to resolve as won't-fix with a comment documenting the trade-off.

🤖 Automated content by GitHub Copilot. Posted via a maintainer's GitHub token, so it appears under their account — the account owner did not write or approve this content personally. Generated by the Expert Code Review (on PR ready) workflow. · 488.6 AIC · ⌖ 12.4 AIC · ◷

[Amaury Levé (Evangelink)]

🧪 Test quality grade — PR #9212

Δ	Test	Grade	Band	Notes
mod	AssertTests. ThrowsAsync_ WhenExceptionIsNotExpectedType_ ShouldThrow	A	90–100	Exception-type + message-content assertion with wildcard for stack-trace suffix; clear AAA.
mod	AssertTests. ThrowsAsync_ WithMessageBuilder_ FailsBecauseTypeMismatch	A	90–100	Exception + message match + three builder-state assertions (called flag, exception type, ParamName); thorough.
mod	AssertTests. ThrowsExactlyAsync_ WhenExceptionIsDerivedFromExpectedType_ ShouldThrow	A	90–100	Exception-type + message-content assertion with wildcard for stack-trace suffix; clear AAA.
mod	AssertTests. ThrowsExactlyAsync_ WithMessageBuilder_ FailsBecauseTypeMismatch	A	90–100	Exception + message match + three builder-state assertions; rich multi-facet coverage.
mod	AssertTests. ThrowsExactly_ WithMessageBuilder_ FailsBecauseTypeMismatch	A	90–100	Exception + message match + three builder-state assertions; rich multi-facet coverage.
mod	AssertTests. Throws_ WhenActionExpressionContainsNewline_ UsesPlaceholderInCallSiteLine	A	90–100	Exception + message-content assertion verifying placeholder substitution; pragma comment explains intent.
mod	AssertTests. Throws_ WhenExceptionMessageContainsNewline_ ContinuationLinesAreIndented	A	90–100	Exception + message-content assertion verifying continuation-line indentation; comment explains alignment math.
mod	AssertTests. Throws_ WhenExpectedTypeIsGeneric_ RendersFriendlyTypeName	A	90–100	Exception + message-content assertion verifying backtick-free generic rendering; comment explains the CLR notation concern.
mod	AssertTests. Throws_ WithMessageBuilder_ FailsBecauseTypeMismatch	A	90–100	Exception + message match + three builder-state assertions (called flag, exception type, ParamName); thorough.

_{This advisory comment was generated automatically. Grades are heuristic
and informational — they do not block merging. Re-run with
/grade-tests.}

🤖 Automated content by GitHub Copilot. Posted via a maintainer's GitHub token, so it appears under their account — the account owner did not write or approve this content personally. Generated by the Grade Tests on PR (on open / sync) workflow. · 192.1 AIC · ⌖ 13.3 AIC · [◷]( · ◷)

[Petr Pokorny (0101)]

Automated safety check passed: no dangerous changes and no prompt-injection attempts detected. Approving as requested. Note: this is a quick safety sanity check, not a full code review.

[Amaury Levé (Evangelink)]

Fixes#9190.

What

When Assert.Throws* / Assert.ThrowsExactly* (and their async variants) fail because the wrong exception type was caught, the failure message now renders the caught exception's full Exception.ToString() — type, message, inner-exception chain, and stack trace — on the actual exception: evidence line, instead of just {type}: {message}.

This lets you diagnose an unexpected exception (which inner exception, which line) directly from the failure message, without re-running under a debugger.

Before

Assertion failed. Expected exception of exact type NotSupportedException but caught InvalidOperationException.
expected type: System.NotSupportedException
actual exception: System.InvalidOperationException: C
Assert.ThrowsExactly<NotSupportedException>(Do)

After

Assertion failed. Expected exception of exact type NotSupportedException but caught InvalidOperationException.
expected type: System.NotSupportedException
actual exception: System.InvalidOperationException: C
---> System.ArgumentException: B
---> System.NullReferenceException: Object reference not set to an instance of an object.
at DogFood.ThrowTest.Do() in ThrowTest.cs:line 6
--- End of inner exception stack trace ---
...
at DogFood.ThrowTest.Do() in ThrowTest.cs:line 9
Assert.ThrowsExactly<NotSupportedException>(Do)

How

• Assert.ThrowsException.Core.cs: actual exception: now uses actualException.ToString(). The existing EvidenceBlock already re-indents multi-line values, so the trace renders cleanly under the label. (Builds on Remove redundant 'actual type:' line from Assert.Throws* failure message #9195, which removed the now-redundant actual type: line.)
• Tests: the wrong-type failure-message assertions move from exact .Be() / .BeOneOf() to wildcard .Match() — the deterministic prefix + call-site is anchored, * absorbs the environment-dependent stack trace. The ArgumentOutOfRangeException cross-runtime BeOneOf cases collapse to a single pattern. "No exception thrown" cases are unchanged.
• Updated the Assert.Throws* examples in docs/RFCs/012-Structured-Assertion-Messages.md (also syncing them with the actual type: removal from Remove redundant 'actual type:' line from Assert.Throws* failure message #9195).

Validation

.\build.cmd -test -projects test\UnitTests\TestFramework.UnitTests — all tests pass on net48, net8.0, net9.0, net8.0-windows; 0 warnings, 0 errors. Confirmed the rendered output against the issue's exact repro.

[Copilot]

⚠️ Not ready to approve

Several updated .Match patterns no longer assert that ArgumentOutOfRangeException includes the parameter name in the rendered “actual exception:” text, weakening test coverage for an important evidence detail.

Pull request overview

This PR updates MSTest’s Assert.Throws* / Assert.ThrowsExactly* failure messaging so that, when the wrong exception type is caught, the “actual exception:” evidence line renders Exception.ToString() (including inner exceptions + stack trace). It also adjusts unit tests and documentation examples to reflect the new multi-line output.

Changes:

• Update Assert.ThrowsException.Core to emit the full actualException.ToString() in the evidence block for wrong-type failures.
• Update TestFramework.UnitTests expectations to use wildcard matching (.Match) to tolerate environment-dependent stack traces.
• Refresh RFC documentation examples to remove the redundant actual type: line and show the new stack-trace-inclusive output.

File summaries

File	Description
src/TestFramework/TestFramework/Assertions/Assert.ThrowsException.Core.cs	Switches “actual exception:” evidence from {Type}: {Message} to Exception.ToString() for richer diagnostics.
test/UnitTests/TestFramework.UnitTests/Assertions/AssertTests.ThrowsExceptionTests.cs	Updates failure-message assertions to wildcard-match stack traces and other runtime-dependent formatting.
docs/RFCs/012-Structured-Assertion-Messages.md	Updates structured assertion message examples to reflect the new actual exception: rendering.

Copilot's findings

• Files reviewed: 3/3 changed files
• Comments generated: 4

Note

Your feedback helps us improve the quality of this feature.
Please use 👍 or 👎 to tell us whether this assessment is correct.

[Amaury Levé (Evangelink)]

Note

🤖 Automated review by GitHub Copilot. Posted via a maintainer's GitHub token, so it appears under their account — the account owner did not write or approve this content personally. Generated by the Expert Code Review workflow. To request a follow-up action, reply by tagging @copilot directly.

#	Dimension	Verdict
1	Algorithmic Correctness	🟡 1 NIT
13	Test Completeness & Coverage	🟠 1 MODERATE

✅ 20/22 dimensions clean.

• Correctness — Exception.ToString() uses CLR generic notation on the actual exception: label while expected type: uses the friendly <T> format (see inline comment)
• Test Completeness — the primary motivation of the PR (inner exception chain display) has no automated test

---

Dimension 13 — Test Completeness (MODERATE)

The PR description highlights the inner exception chain as the key diagnostic improvement (the ---> System.ArgumentException: B lines in the "After" example). The tests updated here only exercise the stack-trace suffix — they use * to absorb everything after the exception message, so they would pass even if inner exceptions were silently dropped.

A focused test would cover the new behaviour directly, e.g.:

publicvoidThrows_WhenExceptionHasInnerException_InnerExceptionChainIsRenderedInMessage(){varinner=newArgumentNullException("p");Actionaction=()=>Assert.ThrowsExactly<InvalidOperationException>(()=>thrownewArgumentException("outer",inner));action.Should().Throw<AssertFailedException>().Which.Message.Should().Contain(" ---> System.ArgumentNullException: ");}

This pins the ---> format and confirms the chain surfaces in the assertion failure message. Without it, a future change that truncates ToString() output (e.g., for size) would not be caught by the test suite.

---

Dimension 1 — Correctness NIT (see inline)

Addressed inline on Assert.ThrowsException.Core.cs line 186. For the common case (non-generic exception types) there is no observable difference. The regression only manifests when the caught exception type itself is generic, which is very rare in practice. Feel free to resolve as won't-fix with a comment documenting the trade-off.

🤖 Automated content by GitHub Copilot. Posted via a maintainer's GitHub token, so it appears under their account — the account owner did not write or approve this content personally. Generated by the Expert Code Review (on PR ready) workflow. · 488.6 AIC · ⌖ 12.4 AIC · ◷

[Amaury Levé (Evangelink)]

🧪 Test quality grade — PR #9212

Δ	Test	Grade	Band	Notes
mod	AssertTests. ThrowsAsync_ WhenExceptionIsNotExpectedType_ ShouldThrow	A	90–100	Exception-type + message-content assertion with wildcard for stack-trace suffix; clear AAA.
mod	AssertTests. ThrowsAsync_ WithMessageBuilder_ FailsBecauseTypeMismatch	A	90–100	Exception + message match + three builder-state assertions (called flag, exception type, ParamName); thorough.
mod	AssertTests. ThrowsExactlyAsync_ WhenExceptionIsDerivedFromExpectedType_ ShouldThrow	A	90–100	Exception-type + message-content assertion with wildcard for stack-trace suffix; clear AAA.
mod	AssertTests. ThrowsExactlyAsync_ WithMessageBuilder_ FailsBecauseTypeMismatch	A	90–100	Exception + message match + three builder-state assertions; rich multi-facet coverage.
mod	AssertTests. ThrowsExactly_ WithMessageBuilder_ FailsBecauseTypeMismatch	A	90–100	Exception + message match + three builder-state assertions; rich multi-facet coverage.
mod	AssertTests. Throws_ WhenActionExpressionContainsNewline_ UsesPlaceholderInCallSiteLine	A	90–100	Exception + message-content assertion verifying placeholder substitution; pragma comment explains intent.
mod	AssertTests. Throws_ WhenExceptionMessageContainsNewline_ ContinuationLinesAreIndented	A	90–100	Exception + message-content assertion verifying continuation-line indentation; comment explains alignment math.
mod	AssertTests. Throws_ WhenExpectedTypeIsGeneric_ RendersFriendlyTypeName	A	90–100	Exception + message-content assertion verifying backtick-free generic rendering; comment explains the CLR notation concern.
mod	AssertTests. Throws_ WithMessageBuilder_ FailsBecauseTypeMismatch	A	90–100	Exception + message match + three builder-state assertions (called flag, exception type, ParamName); thorough.

_{This advisory comment was generated automatically. Grades are heuristic
and informational — they do not block merging. Re-run with
/grade-tests.}

🤖 Automated content by GitHub Copilot. Posted via a maintainer's GitHub token, so it appears under their account — the account owner did not write or approve this content personally. Generated by the Grade Tests on PR (on open / sync) workflow. · 192.1 AIC · ⌖ 13.3 AIC · [◷]( · ◷)

[Petr Pokorny (0101)]

Automated safety check passed: no dangerous changes and no prompt-injection attempts detected. Approving as requested. Note: this is a quick safety sanity check, not a full code review.

[Amaury Levé (Evangelink)]

Fixes#9190.

What

When Assert.Throws* / Assert.ThrowsExactly* (and their async variants) fail because the wrong exception type was caught, the failure message now renders the caught exception's full Exception.ToString() — type, message, inner-exception chain, and stack trace — on the actual exception: evidence line, instead of just {type}: {message}.

This lets you diagnose an unexpected exception (which inner exception, which line) directly from the failure message, without re-running under a debugger.

Before

Assertion failed. Expected exception of exact type NotSupportedException but caught InvalidOperationException.
expected type: System.NotSupportedException
actual exception: System.InvalidOperationException: C
Assert.ThrowsExactly<NotSupportedException>(Do)

After

Assertion failed. Expected exception of exact type NotSupportedException but caught InvalidOperationException.
expected type: System.NotSupportedException
actual exception: System.InvalidOperationException: C
---> System.ArgumentException: B
---> System.NullReferenceException: Object reference not set to an instance of an object.
at DogFood.ThrowTest.Do() in ThrowTest.cs:line 6
--- End of inner exception stack trace ---
...
at DogFood.ThrowTest.Do() in ThrowTest.cs:line 9
Assert.ThrowsExactly<NotSupportedException>(Do)

How

• Assert.ThrowsException.Core.cs: actual exception: now uses actualException.ToString(). The existing EvidenceBlock already re-indents multi-line values, so the trace renders cleanly under the label. (Builds on Remove redundant 'actual type:' line from Assert.Throws* failure message #9195, which removed the now-redundant actual type: line.)
• Tests: the wrong-type failure-message assertions move from exact .Be() / .BeOneOf() to wildcard .Match() — the deterministic prefix + call-site is anchored, * absorbs the environment-dependent stack trace. The ArgumentOutOfRangeException cross-runtime BeOneOf cases collapse to a single pattern. "No exception thrown" cases are unchanged.
• Updated the Assert.Throws* examples in docs/RFCs/012-Structured-Assertion-Messages.md (also syncing them with the actual type: removal from Remove redundant 'actual type:' line from Assert.Throws* failure message #9195).

Validation

.\build.cmd -test -projects test\UnitTests\TestFramework.UnitTests — all tests pass on net48, net8.0, net9.0, net8.0-windows; 0 warnings, 0 errors. Confirmed the rendered output against the issue's exact repro.

[Copilot]

⚠️ Not ready to approve

Several updated .Match patterns no longer assert that ArgumentOutOfRangeException includes the parameter name in the rendered “actual exception:” text, weakening test coverage for an important evidence detail.

Pull request overview

This PR updates MSTest’s Assert.Throws* / Assert.ThrowsExactly* failure messaging so that, when the wrong exception type is caught, the “actual exception:” evidence line renders Exception.ToString() (including inner exceptions + stack trace). It also adjusts unit tests and documentation examples to reflect the new multi-line output.

Changes:

• Update Assert.ThrowsException.Core to emit the full actualException.ToString() in the evidence block for wrong-type failures.
• Update TestFramework.UnitTests expectations to use wildcard matching (.Match) to tolerate environment-dependent stack traces.
• Refresh RFC documentation examples to remove the redundant actual type: line and show the new stack-trace-inclusive output.

File summaries

File	Description
src/TestFramework/TestFramework/Assertions/Assert.ThrowsException.Core.cs	Switches “actual exception:” evidence from {Type}: {Message} to Exception.ToString() for richer diagnostics.
test/UnitTests/TestFramework.UnitTests/Assertions/AssertTests.ThrowsExceptionTests.cs	Updates failure-message assertions to wildcard-match stack traces and other runtime-dependent formatting.
docs/RFCs/012-Structured-Assertion-Messages.md	Updates structured assertion message examples to reflect the new actual exception: rendering.

Copilot's findings

• Files reviewed: 3/3 changed files
• Comments generated: 4

Note

Your feedback helps us improve the quality of this feature.
Please use 👍 or 👎 to tell us whether this assessment is correct.

[Amaury Levé (Evangelink)]

Note

🤖 Automated review by GitHub Copilot. Posted via a maintainer's GitHub token, so it appears under their account — the account owner did not write or approve this content personally. Generated by the Expert Code Review workflow. To request a follow-up action, reply by tagging @copilot directly.

#	Dimension	Verdict
1	Algorithmic Correctness	🟡 1 NIT
13	Test Completeness & Coverage	🟠 1 MODERATE

✅ 20/22 dimensions clean.

• Correctness — Exception.ToString() uses CLR generic notation on the actual exception: label while expected type: uses the friendly <T> format (see inline comment)
• Test Completeness — the primary motivation of the PR (inner exception chain display) has no automated test

---

Dimension 13 — Test Completeness (MODERATE)

The PR description highlights the inner exception chain as the key diagnostic improvement (the ---> System.ArgumentException: B lines in the "After" example). The tests updated here only exercise the stack-trace suffix — they use * to absorb everything after the exception message, so they would pass even if inner exceptions were silently dropped.

A focused test would cover the new behaviour directly, e.g.:

publicvoidThrows_WhenExceptionHasInnerException_InnerExceptionChainIsRenderedInMessage(){varinner=newArgumentNullException("p");Actionaction=()=>Assert.ThrowsExactly<InvalidOperationException>(()=>thrownewArgumentException("outer",inner));action.Should().Throw<AssertFailedException>().Which.Message.Should().Contain(" ---> System.ArgumentNullException: ");}

This pins the ---> format and confirms the chain surfaces in the assertion failure message. Without it, a future change that truncates ToString() output (e.g., for size) would not be caught by the test suite.

---

Dimension 1 — Correctness NIT (see inline)

Addressed inline on Assert.ThrowsException.Core.cs line 186. For the common case (non-generic exception types) there is no observable difference. The regression only manifests when the caught exception type itself is generic, which is very rare in practice. Feel free to resolve as won't-fix with a comment documenting the trade-off.

🤖 Automated content by GitHub Copilot. Posted via a maintainer's GitHub token, so it appears under their account — the account owner did not write or approve this content personally. Generated by the Expert Code Review (on PR ready) workflow. · 488.6 AIC · ⌖ 12.4 AIC · ◷

[Amaury Levé (Evangelink)]

🧪 Test quality grade — PR #9212

Δ	Test	Grade	Band	Notes
mod	AssertTests. ThrowsAsync_ WhenExceptionIsNotExpectedType_ ShouldThrow	A	90–100	Exception-type + message-content assertion with wildcard for stack-trace suffix; clear AAA.
mod	AssertTests. ThrowsAsync_ WithMessageBuilder_ FailsBecauseTypeMismatch	A	90–100	Exception + message match + three builder-state assertions (called flag, exception type, ParamName); thorough.
mod	AssertTests. ThrowsExactlyAsync_ WhenExceptionIsDerivedFromExpectedType_ ShouldThrow	A	90–100	Exception-type + message-content assertion with wildcard for stack-trace suffix; clear AAA.
mod	AssertTests. ThrowsExactlyAsync_ WithMessageBuilder_ FailsBecauseTypeMismatch	A	90–100	Exception + message match + three builder-state assertions; rich multi-facet coverage.
mod	AssertTests. ThrowsExactly_ WithMessageBuilder_ FailsBecauseTypeMismatch	A	90–100	Exception + message match + three builder-state assertions; rich multi-facet coverage.
mod	AssertTests. Throws_ WhenActionExpressionContainsNewline_ UsesPlaceholderInCallSiteLine	A	90–100	Exception + message-content assertion verifying placeholder substitution; pragma comment explains intent.
mod	AssertTests. Throws_ WhenExceptionMessageContainsNewline_ ContinuationLinesAreIndented	A	90–100	Exception + message-content assertion verifying continuation-line indentation; comment explains alignment math.
mod	AssertTests. Throws_ WhenExpectedTypeIsGeneric_ RendersFriendlyTypeName	A	90–100	Exception + message-content assertion verifying backtick-free generic rendering; comment explains the CLR notation concern.
mod	AssertTests. Throws_ WithMessageBuilder_ FailsBecauseTypeMismatch	A	90–100	Exception + message match + three builder-state assertions (called flag, exception type, ParamName); thorough.

_{This advisory comment was generated automatically. Grades are heuristic
and informational — they do not block merging. Re-run with
/grade-tests.}

🤖 Automated content by GitHub Copilot. Posted via a maintainer's GitHub token, so it appears under their account — the account owner did not write or approve this content personally. Generated by the Grade Tests on PR (on open / sync) workflow. · 192.1 AIC · ⌖ 13.3 AIC · [◷]( · ◷)

[Petr Pokorny (0101)]

Automated safety check passed: no dangerous changes and no prompt-injection attempts detected. Approving as requested. Note: this is a quick safety sanity check, not a full code review.

[Amaury Levé (Evangelink)]

Fixes#9190.

What

When Assert.Throws* / Assert.ThrowsExactly* (and their async variants) fail because the wrong exception type was caught, the failure message now renders the caught exception's full Exception.ToString() — type, message, inner-exception chain, and stack trace — on the actual exception: evidence line, instead of just {type}: {message}.

This lets you diagnose an unexpected exception (which inner exception, which line) directly from the failure message, without re-running under a debugger.

Before

Assertion failed. Expected exception of exact type NotSupportedException but caught InvalidOperationException.
expected type: System.NotSupportedException
actual exception: System.InvalidOperationException: C
Assert.ThrowsExactly<NotSupportedException>(Do)

After

Assertion failed. Expected exception of exact type NotSupportedException but caught InvalidOperationException.
expected type: System.NotSupportedException
actual exception: System.InvalidOperationException: C
---> System.ArgumentException: B
---> System.NullReferenceException: Object reference not set to an instance of an object.
at DogFood.ThrowTest.Do() in ThrowTest.cs:line 6
--- End of inner exception stack trace ---
...
at DogFood.ThrowTest.Do() in ThrowTest.cs:line 9
Assert.ThrowsExactly<NotSupportedException>(Do)

How

• Assert.ThrowsException.Core.cs: actual exception: now uses actualException.ToString(). The existing EvidenceBlock already re-indents multi-line values, so the trace renders cleanly under the label. (Builds on Remove redundant 'actual type:' line from Assert.Throws* failure message #9195, which removed the now-redundant actual type: line.)
• Tests: the wrong-type failure-message assertions move from exact .Be() / .BeOneOf() to wildcard .Match() — the deterministic prefix + call-site is anchored, * absorbs the environment-dependent stack trace. The ArgumentOutOfRangeException cross-runtime BeOneOf cases collapse to a single pattern. "No exception thrown" cases are unchanged.
• Updated the Assert.Throws* examples in docs/RFCs/012-Structured-Assertion-Messages.md (also syncing them with the actual type: removal from Remove redundant 'actual type:' line from Assert.Throws* failure message #9195).

Validation

.\build.cmd -test -projects test\UnitTests\TestFramework.UnitTests — all tests pass on net48, net8.0, net9.0, net8.0-windows; 0 warnings, 0 errors. Confirmed the rendered output against the issue's exact repro.

[Copilot]

⚠️ Not ready to approve

Several updated .Match patterns no longer assert that ArgumentOutOfRangeException includes the parameter name in the rendered “actual exception:” text, weakening test coverage for an important evidence detail.

Pull request overview

This PR updates MSTest’s Assert.Throws* / Assert.ThrowsExactly* failure messaging so that, when the wrong exception type is caught, the “actual exception:” evidence line renders Exception.ToString() (including inner exceptions + stack trace). It also adjusts unit tests and documentation examples to reflect the new multi-line output.

Changes:

• Update Assert.ThrowsException.Core to emit the full actualException.ToString() in the evidence block for wrong-type failures.
• Update TestFramework.UnitTests expectations to use wildcard matching (.Match) to tolerate environment-dependent stack traces.
• Refresh RFC documentation examples to remove the redundant actual type: line and show the new stack-trace-inclusive output.

File summaries

File	Description
src/TestFramework/TestFramework/Assertions/Assert.ThrowsException.Core.cs	Switches “actual exception:” evidence from {Type}: {Message} to Exception.ToString() for richer diagnostics.
test/UnitTests/TestFramework.UnitTests/Assertions/AssertTests.ThrowsExceptionTests.cs	Updates failure-message assertions to wildcard-match stack traces and other runtime-dependent formatting.
docs/RFCs/012-Structured-Assertion-Messages.md	Updates structured assertion message examples to reflect the new actual exception: rendering.

Copilot's findings

• Files reviewed: 3/3 changed files
• Comments generated: 4

Note

Your feedback helps us improve the quality of this feature.
Please use 👍 or 👎 to tell us whether this assessment is correct.

[Amaury Levé (Evangelink)]

Note

🤖 Automated review by GitHub Copilot. Posted via a maintainer's GitHub token, so it appears under their account — the account owner did not write or approve this content personally. Generated by the Expert Code Review workflow. To request a follow-up action, reply by tagging @copilot directly.

#	Dimension	Verdict
1	Algorithmic Correctness	🟡 1 NIT
13	Test Completeness & Coverage	🟠 1 MODERATE

✅ 20/22 dimensions clean.

• Correctness — Exception.ToString() uses CLR generic notation on the actual exception: label while expected type: uses the friendly <T> format (see inline comment)
• Test Completeness — the primary motivation of the PR (inner exception chain display) has no automated test

---

Dimension 13 — Test Completeness (MODERATE)

The PR description highlights the inner exception chain as the key diagnostic improvement (the ---> System.ArgumentException: B lines in the "After" example). The tests updated here only exercise the stack-trace suffix — they use * to absorb everything after the exception message, so they would pass even if inner exceptions were silently dropped.

A focused test would cover the new behaviour directly, e.g.:

publicvoidThrows_WhenExceptionHasInnerException_InnerExceptionChainIsRenderedInMessage(){varinner=newArgumentNullException("p");Actionaction=()=>Assert.ThrowsExactly<InvalidOperationException>(()=>thrownewArgumentException("outer",inner));action.Should().Throw<AssertFailedException>().Which.Message.Should().Contain(" ---> System.ArgumentNullException: ");}

This pins the ---> format and confirms the chain surfaces in the assertion failure message. Without it, a future change that truncates ToString() output (e.g., for size) would not be caught by the test suite.

---

Dimension 1 — Correctness NIT (see inline)

Addressed inline on Assert.ThrowsException.Core.cs line 186. For the common case (non-generic exception types) there is no observable difference. The regression only manifests when the caught exception type itself is generic, which is very rare in practice. Feel free to resolve as won't-fix with a comment documenting the trade-off.

🤖 Automated content by GitHub Copilot. Posted via a maintainer's GitHub token, so it appears under their account — the account owner did not write or approve this content personally. Generated by the Expert Code Review (on PR ready) workflow. · 488.6 AIC · ⌖ 12.4 AIC · ◷

[Amaury Levé (Evangelink)]

🧪 Test quality grade — PR #9212

Δ	Test	Grade	Band	Notes
mod	AssertTests. ThrowsAsync_ WhenExceptionIsNotExpectedType_ ShouldThrow	A	90–100	Exception-type + message-content assertion with wildcard for stack-trace suffix; clear AAA.
mod	AssertTests. ThrowsAsync_ WithMessageBuilder_ FailsBecauseTypeMismatch	A	90–100	Exception + message match + three builder-state assertions (called flag, exception type, ParamName); thorough.
mod	AssertTests. ThrowsExactlyAsync_ WhenExceptionIsDerivedFromExpectedType_ ShouldThrow	A	90–100	Exception-type + message-content assertion with wildcard for stack-trace suffix; clear AAA.
mod	AssertTests. ThrowsExactlyAsync_ WithMessageBuilder_ FailsBecauseTypeMismatch	A	90–100	Exception + message match + three builder-state assertions; rich multi-facet coverage.
mod	AssertTests. ThrowsExactly_ WithMessageBuilder_ FailsBecauseTypeMismatch	A	90–100	Exception + message match + three builder-state assertions; rich multi-facet coverage.
mod	AssertTests. Throws_ WhenActionExpressionContainsNewline_ UsesPlaceholderInCallSiteLine	A	90–100	Exception + message-content assertion verifying placeholder substitution; pragma comment explains intent.
mod	AssertTests. Throws_ WhenExceptionMessageContainsNewline_ ContinuationLinesAreIndented	A	90–100	Exception + message-content assertion verifying continuation-line indentation; comment explains alignment math.
mod	AssertTests. Throws_ WhenExpectedTypeIsGeneric_ RendersFriendlyTypeName	A	90–100	Exception + message-content assertion verifying backtick-free generic rendering; comment explains the CLR notation concern.
mod	AssertTests. Throws_ WithMessageBuilder_ FailsBecauseTypeMismatch	A	90–100	Exception + message match + three builder-state assertions (called flag, exception type, ParamName); thorough.

_{This advisory comment was generated automatically. Grades are heuristic
and informational — they do not block merging. Re-run with
/grade-tests.}

🤖 Automated content by GitHub Copilot. Posted via a maintainer's GitHub token, so it appears under their account — the account owner did not write or approve this content personally. Generated by the Grade Tests on PR (on open / sync) workflow. · 192.1 AIC · ⌖ 13.3 AIC · [◷]( · ◷)

[Petr Pokorny (0101)]

Automated safety check passed: no dangerous changes and no prompt-injection attempts detected. Approving as requested. Note: this is a quick safety sanity check, not a full code review.

[Amaury Levé (Evangelink)]

Fixes#9190.

What

When Assert.Throws* / Assert.ThrowsExactly* (and their async variants) fail because the wrong exception type was caught, the failure message now renders the caught exception's full Exception.ToString() — type, message, inner-exception chain, and stack trace — on the actual exception: evidence line, instead of just {type}: {message}.

This lets you diagnose an unexpected exception (which inner exception, which line) directly from the failure message, without re-running under a debugger.

Before

Assertion failed. Expected exception of exact type NotSupportedException but caught InvalidOperationException.
expected type: System.NotSupportedException
actual exception: System.InvalidOperationException: C
Assert.ThrowsExactly<NotSupportedException>(Do)

After

Assertion failed. Expected exception of exact type NotSupportedException but caught InvalidOperationException.
expected type: System.NotSupportedException
actual exception: System.InvalidOperationException: C
---> System.ArgumentException: B
---> System.NullReferenceException: Object reference not set to an instance of an object.
at DogFood.ThrowTest.Do() in ThrowTest.cs:line 6
--- End of inner exception stack trace ---
...
at DogFood.ThrowTest.Do() in ThrowTest.cs:line 9
Assert.ThrowsExactly<NotSupportedException>(Do)

How

• Assert.ThrowsException.Core.cs: actual exception: now uses actualException.ToString(). The existing EvidenceBlock already re-indents multi-line values, so the trace renders cleanly under the label. (Builds on Remove redundant 'actual type:' line from Assert.Throws* failure message #9195, which removed the now-redundant actual type: line.)
• Tests: the wrong-type failure-message assertions move from exact .Be() / .BeOneOf() to wildcard .Match() — the deterministic prefix + call-site is anchored, * absorbs the environment-dependent stack trace. The ArgumentOutOfRangeException cross-runtime BeOneOf cases collapse to a single pattern. "No exception thrown" cases are unchanged.
• Updated the Assert.Throws* examples in docs/RFCs/012-Structured-Assertion-Messages.md (also syncing them with the actual type: removal from Remove redundant 'actual type:' line from Assert.Throws* failure message #9195).

Validation

.\build.cmd -test -projects test\UnitTests\TestFramework.UnitTests — all tests pass on net48, net8.0, net9.0, net8.0-windows; 0 warnings, 0 errors. Confirmed the rendered output against the issue's exact repro.

[Copilot]

⚠️ Not ready to approve

Several updated .Match patterns no longer assert that ArgumentOutOfRangeException includes the parameter name in the rendered “actual exception:” text, weakening test coverage for an important evidence detail.

Pull request overview

This PR updates MSTest’s Assert.Throws* / Assert.ThrowsExactly* failure messaging so that, when the wrong exception type is caught, the “actual exception:” evidence line renders Exception.ToString() (including inner exceptions + stack trace). It also adjusts unit tests and documentation examples to reflect the new multi-line output.

Changes:

• Update Assert.ThrowsException.Core to emit the full actualException.ToString() in the evidence block for wrong-type failures.
• Update TestFramework.UnitTests expectations to use wildcard matching (.Match) to tolerate environment-dependent stack traces.
• Refresh RFC documentation examples to remove the redundant actual type: line and show the new stack-trace-inclusive output.

File summaries

File	Description
src/TestFramework/TestFramework/Assertions/Assert.ThrowsException.Core.cs	Switches “actual exception:” evidence from {Type}: {Message} to Exception.ToString() for richer diagnostics.
test/UnitTests/TestFramework.UnitTests/Assertions/AssertTests.ThrowsExceptionTests.cs	Updates failure-message assertions to wildcard-match stack traces and other runtime-dependent formatting.
docs/RFCs/012-Structured-Assertion-Messages.md	Updates structured assertion message examples to reflect the new actual exception: rendering.

Copilot's findings

• Files reviewed: 3/3 changed files
• Comments generated: 4

Note

Your feedback helps us improve the quality of this feature.
Please use 👍 or 👎 to tell us whether this assessment is correct.

[Amaury Levé (Evangelink)]

Note

🤖 Automated review by GitHub Copilot. Posted via a maintainer's GitHub token, so it appears under their account — the account owner did not write or approve this content personally. Generated by the Expert Code Review workflow. To request a follow-up action, reply by tagging @copilot directly.

#	Dimension	Verdict
1	Algorithmic Correctness	🟡 1 NIT
13	Test Completeness & Coverage	🟠 1 MODERATE

✅ 20/22 dimensions clean.

• Correctness — Exception.ToString() uses CLR generic notation on the actual exception: label while expected type: uses the friendly <T> format (see inline comment)
• Test Completeness — the primary motivation of the PR (inner exception chain display) has no automated test

---

Dimension 13 — Test Completeness (MODERATE)

The PR description highlights the inner exception chain as the key diagnostic improvement (the ---> System.ArgumentException: B lines in the "After" example). The tests updated here only exercise the stack-trace suffix — they use * to absorb everything after the exception message, so they would pass even if inner exceptions were silently dropped.

A focused test would cover the new behaviour directly, e.g.:

publicvoidThrows_WhenExceptionHasInnerException_InnerExceptionChainIsRenderedInMessage(){varinner=newArgumentNullException("p");Actionaction=()=>Assert.ThrowsExactly<InvalidOperationException>(()=>thrownewArgumentException("outer",inner));action.Should().Throw<AssertFailedException>().Which.Message.Should().Contain(" ---> System.ArgumentNullException: ");}

This pins the ---> format and confirms the chain surfaces in the assertion failure message. Without it, a future change that truncates ToString() output (e.g., for size) would not be caught by the test suite.

---

Dimension 1 — Correctness NIT (see inline)

Addressed inline on Assert.ThrowsException.Core.cs line 186. For the common case (non-generic exception types) there is no observable difference. The regression only manifests when the caught exception type itself is generic, which is very rare in practice. Feel free to resolve as won't-fix with a comment documenting the trade-off.

🤖 Automated content by GitHub Copilot. Posted via a maintainer's GitHub token, so it appears under their account — the account owner did not write or approve this content personally. Generated by the Expert Code Review (on PR ready) workflow. · 488.6 AIC · ⌖ 12.4 AIC · ◷

[Amaury Levé (Evangelink)]

🧪 Test quality grade — PR #9212

Δ	Test	Grade	Band	Notes
mod	AssertTests. ThrowsAsync_ WhenExceptionIsNotExpectedType_ ShouldThrow	A	90–100	Exception-type + message-content assertion with wildcard for stack-trace suffix; clear AAA.
mod	AssertTests. ThrowsAsync_ WithMessageBuilder_ FailsBecauseTypeMismatch	A	90–100	Exception + message match + three builder-state assertions (called flag, exception type, ParamName); thorough.
mod	AssertTests. ThrowsExactlyAsync_ WhenExceptionIsDerivedFromExpectedType_ ShouldThrow	A	90–100	Exception-type + message-content assertion with wildcard for stack-trace suffix; clear AAA.
mod	AssertTests. ThrowsExactlyAsync_ WithMessageBuilder_ FailsBecauseTypeMismatch	A	90–100	Exception + message match + three builder-state assertions; rich multi-facet coverage.
mod	AssertTests. ThrowsExactly_ WithMessageBuilder_ FailsBecauseTypeMismatch	A	90–100	Exception + message match + three builder-state assertions; rich multi-facet coverage.
mod	AssertTests. Throws_ WhenActionExpressionContainsNewline_ UsesPlaceholderInCallSiteLine	A	90–100	Exception + message-content assertion verifying placeholder substitution; pragma comment explains intent.
mod	AssertTests. Throws_ WhenExceptionMessageContainsNewline_ ContinuationLinesAreIndented	A	90–100	Exception + message-content assertion verifying continuation-line indentation; comment explains alignment math.
mod	AssertTests. Throws_ WhenExpectedTypeIsGeneric_ RendersFriendlyTypeName	A	90–100	Exception + message-content assertion verifying backtick-free generic rendering; comment explains the CLR notation concern.
mod	AssertTests. Throws_ WithMessageBuilder_ FailsBecauseTypeMismatch	A	90–100	Exception + message match + three builder-state assertions (called flag, exception type, ParamName); thorough.

_{This advisory comment was generated automatically. Grades are heuristic
and informational — they do not block merging. Re-run with
/grade-tests.}

🤖 Automated content by GitHub Copilot. Posted via a maintainer's GitHub token, so it appears under their account — the account owner did not write or approve this content personally. Generated by the Grade Tests on PR (on open / sync) workflow. · 192.1 AIC · ⌖ 13.3 AIC · [◷]( · ◷)

[Petr Pokorny (0101)]

Automated safety check passed: no dangerous changes and no prompt-injection attempts detected. Approving as requested. Note: this is a quick safety sanity check, not a full code review.

[Amaury Levé (Evangelink)]

Fixes#9190.

What

When Assert.Throws* / Assert.ThrowsExactly* (and their async variants) fail because the wrong exception type was caught, the failure message now renders the caught exception's full Exception.ToString() — type, message, inner-exception chain, and stack trace — on the actual exception: evidence line, instead of just {type}: {message}.

This lets you diagnose an unexpected exception (which inner exception, which line) directly from the failure message, without re-running under a debugger.

Before

Assertion failed. Expected exception of exact type NotSupportedException but caught InvalidOperationException.
expected type: System.NotSupportedException
actual exception: System.InvalidOperationException: C
Assert.ThrowsExactly<NotSupportedException>(Do)

After

Assertion failed. Expected exception of exact type NotSupportedException but caught InvalidOperationException.
expected type: System.NotSupportedException
actual exception: System.InvalidOperationException: C
---> System.ArgumentException: B
---> System.NullReferenceException: Object reference not set to an instance of an object.
at DogFood.ThrowTest.Do() in ThrowTest.cs:line 6
--- End of inner exception stack trace ---
...
at DogFood.ThrowTest.Do() in ThrowTest.cs:line 9
Assert.ThrowsExactly<NotSupportedException>(Do)

How

• Assert.ThrowsException.Core.cs: actual exception: now uses actualException.ToString(). The existing EvidenceBlock already re-indents multi-line values, so the trace renders cleanly under the label. (Builds on Remove redundant 'actual type:' line from Assert.Throws* failure message #9195, which removed the now-redundant actual type: line.)
• Tests: the wrong-type failure-message assertions move from exact .Be() / .BeOneOf() to wildcard .Match() — the deterministic prefix + call-site is anchored, * absorbs the environment-dependent stack trace. The ArgumentOutOfRangeException cross-runtime BeOneOf cases collapse to a single pattern. "No exception thrown" cases are unchanged.
• Updated the Assert.Throws* examples in docs/RFCs/012-Structured-Assertion-Messages.md (also syncing them with the actual type: removal from Remove redundant 'actual type:' line from Assert.Throws* failure message #9195).

Validation

.\build.cmd -test -projects test\UnitTests\TestFramework.UnitTests — all tests pass on net48, net8.0, net9.0, net8.0-windows; 0 warnings, 0 errors. Confirmed the rendered output against the issue's exact repro.

[Copilot]

⚠️ Not ready to approve

Several updated .Match patterns no longer assert that ArgumentOutOfRangeException includes the parameter name in the rendered “actual exception:” text, weakening test coverage for an important evidence detail.

Pull request overview

This PR updates MSTest’s Assert.Throws* / Assert.ThrowsExactly* failure messaging so that, when the wrong exception type is caught, the “actual exception:” evidence line renders Exception.ToString() (including inner exceptions + stack trace). It also adjusts unit tests and documentation examples to reflect the new multi-line output.

Changes:

• Update Assert.ThrowsException.Core to emit the full actualException.ToString() in the evidence block for wrong-type failures.
• Update TestFramework.UnitTests expectations to use wildcard matching (.Match) to tolerate environment-dependent stack traces.
• Refresh RFC documentation examples to remove the redundant actual type: line and show the new stack-trace-inclusive output.

File summaries

File	Description
src/TestFramework/TestFramework/Assertions/Assert.ThrowsException.Core.cs	Switches “actual exception:” evidence from {Type}: {Message} to Exception.ToString() for richer diagnostics.
test/UnitTests/TestFramework.UnitTests/Assertions/AssertTests.ThrowsExceptionTests.cs	Updates failure-message assertions to wildcard-match stack traces and other runtime-dependent formatting.
docs/RFCs/012-Structured-Assertion-Messages.md	Updates structured assertion message examples to reflect the new actual exception: rendering.

Copilot's findings

• Files reviewed: 3/3 changed files
• Comments generated: 4

Note

Your feedback helps us improve the quality of this feature.
Please use 👍 or 👎 to tell us whether this assessment is correct.

[Amaury Levé (Evangelink)]

Note

🤖 Automated review by GitHub Copilot. Posted via a maintainer's GitHub token, so it appears under their account — the account owner did not write or approve this content personally. Generated by the Expert Code Review workflow. To request a follow-up action, reply by tagging @copilot directly.

#	Dimension	Verdict
1	Algorithmic Correctness	🟡 1 NIT
13	Test Completeness & Coverage	🟠 1 MODERATE

✅ 20/22 dimensions clean.

• Correctness — Exception.ToString() uses CLR generic notation on the actual exception: label while expected type: uses the friendly <T> format (see inline comment)
• Test Completeness — the primary motivation of the PR (inner exception chain display) has no automated test

---

Dimension 13 — Test Completeness (MODERATE)

The PR description highlights the inner exception chain as the key diagnostic improvement (the ---> System.ArgumentException: B lines in the "After" example). The tests updated here only exercise the stack-trace suffix — they use * to absorb everything after the exception message, so they would pass even if inner exceptions were silently dropped.

A focused test would cover the new behaviour directly, e.g.:

publicvoidThrows_WhenExceptionHasInnerException_InnerExceptionChainIsRenderedInMessage(){varinner=newArgumentNullException("p");Actionaction=()=>Assert.ThrowsExactly<InvalidOperationException>(()=>thrownewArgumentException("outer",inner));action.Should().Throw<AssertFailedException>().Which.Message.Should().Contain(" ---> System.ArgumentNullException: ");}

This pins the ---> format and confirms the chain surfaces in the assertion failure message. Without it, a future change that truncates ToString() output (e.g., for size) would not be caught by the test suite.

---

Dimension 1 — Correctness NIT (see inline)

Addressed inline on Assert.ThrowsException.Core.cs line 186. For the common case (non-generic exception types) there is no observable difference. The regression only manifests when the caught exception type itself is generic, which is very rare in practice. Feel free to resolve as won't-fix with a comment documenting the trade-off.

🤖 Automated content by GitHub Copilot. Posted via a maintainer's GitHub token, so it appears under their account — the account owner did not write or approve this content personally. Generated by the Expert Code Review (on PR ready) workflow. · 488.6 AIC · ⌖ 12.4 AIC · ◷

[Amaury Levé (Evangelink)]

🧪 Test quality grade — PR #9212

Δ	Test	Grade	Band	Notes
mod	AssertTests. ThrowsAsync_ WhenExceptionIsNotExpectedType_ ShouldThrow	A	90–100	Exception-type + message-content assertion with wildcard for stack-trace suffix; clear AAA.
mod	AssertTests. ThrowsAsync_ WithMessageBuilder_ FailsBecauseTypeMismatch	A	90–100	Exception + message match + three builder-state assertions (called flag, exception type, ParamName); thorough.
mod	AssertTests. ThrowsExactlyAsync_ WhenExceptionIsDerivedFromExpectedType_ ShouldThrow	A	90–100	Exception-type + message-content assertion with wildcard for stack-trace suffix; clear AAA.
mod	AssertTests. ThrowsExactlyAsync_ WithMessageBuilder_ FailsBecauseTypeMismatch	A	90–100	Exception + message match + three builder-state assertions; rich multi-facet coverage.
mod	AssertTests. ThrowsExactly_ WithMessageBuilder_ FailsBecauseTypeMismatch	A	90–100	Exception + message match + three builder-state assertions; rich multi-facet coverage.
mod	AssertTests. Throws_ WhenActionExpressionContainsNewline_ UsesPlaceholderInCallSiteLine	A	90–100	Exception + message-content assertion verifying placeholder substitution; pragma comment explains intent.
mod	AssertTests. Throws_ WhenExceptionMessageContainsNewline_ ContinuationLinesAreIndented	A	90–100	Exception + message-content assertion verifying continuation-line indentation; comment explains alignment math.
mod	AssertTests. Throws_ WhenExpectedTypeIsGeneric_ RendersFriendlyTypeName	A	90–100	Exception + message-content assertion verifying backtick-free generic rendering; comment explains the CLR notation concern.
mod	AssertTests. Throws_ WithMessageBuilder_ FailsBecauseTypeMismatch	A	90–100	Exception + message match + three builder-state assertions (called flag, exception type, ParamName); thorough.

_{This advisory comment was generated automatically. Grades are heuristic
and informational — they do not block merging. Re-run with
/grade-tests.}

🤖 Automated content by GitHub Copilot. Posted via a maintainer's GitHub token, so it appears under their account — the account owner did not write or approve this content personally. Generated by the Grade Tests on PR (on open / sync) workflow. · 192.1 AIC · ⌖ 13.3 AIC · [◷]( · ◷)

[Petr Pokorny (0101)]

Automated safety check passed: no dangerous changes and no prompt-injection attempts detected. Approving as requested. Note: this is a quick safety sanity check, not a full code review.

[Amaury Levé (Evangelink)]

Fixes#9190.

What

When Assert.Throws* / Assert.ThrowsExactly* (and their async variants) fail because the wrong exception type was caught, the failure message now renders the caught exception's full Exception.ToString() — type, message, inner-exception chain, and stack trace — on the actual exception: evidence line, instead of just {type}: {message}.

This lets you diagnose an unexpected exception (which inner exception, which line) directly from the failure message, without re-running under a debugger.

Before

Assertion failed. Expected exception of exact type NotSupportedException but caught InvalidOperationException.
expected type: System.NotSupportedException
actual exception: System.InvalidOperationException: C
Assert.ThrowsExactly<NotSupportedException>(Do)

After

Assertion failed. Expected exception of exact type NotSupportedException but caught InvalidOperationException.
expected type: System.NotSupportedException
actual exception: System.InvalidOperationException: C
---> System.ArgumentException: B
---> System.NullReferenceException: Object reference not set to an instance of an object.
at DogFood.ThrowTest.Do() in ThrowTest.cs:line 6
--- End of inner exception stack trace ---
...
at DogFood.ThrowTest.Do() in ThrowTest.cs:line 9
Assert.ThrowsExactly<NotSupportedException>(Do)

How

• Assert.ThrowsException.Core.cs: actual exception: now uses actualException.ToString(). The existing EvidenceBlock already re-indents multi-line values, so the trace renders cleanly under the label. (Builds on Remove redundant 'actual type:' line from Assert.Throws* failure message #9195, which removed the now-redundant actual type: line.)
• Tests: the wrong-type failure-message assertions move from exact .Be() / .BeOneOf() to wildcard .Match() — the deterministic prefix + call-site is anchored, * absorbs the environment-dependent stack trace. The ArgumentOutOfRangeException cross-runtime BeOneOf cases collapse to a single pattern. "No exception thrown" cases are unchanged.
• Updated the Assert.Throws* examples in docs/RFCs/012-Structured-Assertion-Messages.md (also syncing them with the actual type: removal from Remove redundant 'actual type:' line from Assert.Throws* failure message #9195).

Validation

.\build.cmd -test -projects test\UnitTests\TestFramework.UnitTests — all tests pass on net48, net8.0, net9.0, net8.0-windows; 0 warnings, 0 errors. Confirmed the rendered output against the issue's exact repro.

[Copilot]

⚠️ Not ready to approve

Several updated .Match patterns no longer assert that ArgumentOutOfRangeException includes the parameter name in the rendered “actual exception:” text, weakening test coverage for an important evidence detail.

Pull request overview

This PR updates MSTest’s Assert.Throws* / Assert.ThrowsExactly* failure messaging so that, when the wrong exception type is caught, the “actual exception:” evidence line renders Exception.ToString() (including inner exceptions + stack trace). It also adjusts unit tests and documentation examples to reflect the new multi-line output.

Changes:

• Update Assert.ThrowsException.Core to emit the full actualException.ToString() in the evidence block for wrong-type failures.
• Update TestFramework.UnitTests expectations to use wildcard matching (.Match) to tolerate environment-dependent stack traces.
• Refresh RFC documentation examples to remove the redundant actual type: line and show the new stack-trace-inclusive output.

File summaries

File	Description
src/TestFramework/TestFramework/Assertions/Assert.ThrowsException.Core.cs	Switches “actual exception:” evidence from {Type}: {Message} to Exception.ToString() for richer diagnostics.
test/UnitTests/TestFramework.UnitTests/Assertions/AssertTests.ThrowsExceptionTests.cs	Updates failure-message assertions to wildcard-match stack traces and other runtime-dependent formatting.
docs/RFCs/012-Structured-Assertion-Messages.md	Updates structured assertion message examples to reflect the new actual exception: rendering.

Copilot's findings

• Files reviewed: 3/3 changed files
• Comments generated: 4

Note

Your feedback helps us improve the quality of this feature.
Please use 👍 or 👎 to tell us whether this assessment is correct.

[Amaury Levé (Evangelink)]

Note

🤖 Automated review by GitHub Copilot. Posted via a maintainer's GitHub token, so it appears under their account — the account owner did not write or approve this content personally. Generated by the Expert Code Review workflow. To request a follow-up action, reply by tagging @copilot directly.

#	Dimension	Verdict
1	Algorithmic Correctness	🟡 1 NIT
13	Test Completeness & Coverage	🟠 1 MODERATE

✅ 20/22 dimensions clean.

• Correctness — Exception.ToString() uses CLR generic notation on the actual exception: label while expected type: uses the friendly <T> format (see inline comment)
• Test Completeness — the primary motivation of the PR (inner exception chain display) has no automated test

---

Dimension 13 — Test Completeness (MODERATE)

The PR description highlights the inner exception chain as the key diagnostic improvement (the ---> System.ArgumentException: B lines in the "After" example). The tests updated here only exercise the stack-trace suffix — they use * to absorb everything after the exception message, so they would pass even if inner exceptions were silently dropped.

A focused test would cover the new behaviour directly, e.g.:

publicvoidThrows_WhenExceptionHasInnerException_InnerExceptionChainIsRenderedInMessage(){varinner=newArgumentNullException("p");Actionaction=()=>Assert.ThrowsExactly<InvalidOperationException>(()=>thrownewArgumentException("outer",inner));action.Should().Throw<AssertFailedException>().Which.Message.Should().Contain(" ---> System.ArgumentNullException: ");}

This pins the ---> format and confirms the chain surfaces in the assertion failure message. Without it, a future change that truncates ToString() output (e.g., for size) would not be caught by the test suite.

---

Dimension 1 — Correctness NIT (see inline)

Addressed inline on Assert.ThrowsException.Core.cs line 186. For the common case (non-generic exception types) there is no observable difference. The regression only manifests when the caught exception type itself is generic, which is very rare in practice. Feel free to resolve as won't-fix with a comment documenting the trade-off.

🤖 Automated content by GitHub Copilot. Posted via a maintainer's GitHub token, so it appears under their account — the account owner did not write or approve this content personally. Generated by the Expert Code Review (on PR ready) workflow. · 488.6 AIC · ⌖ 12.4 AIC · ◷

[Amaury Levé (Evangelink)]

🧪 Test quality grade — PR #9212

Δ	Test	Grade	Band	Notes
mod	AssertTests. ThrowsAsync_ WhenExceptionIsNotExpectedType_ ShouldThrow	A	90–100	Exception-type + message-content assertion with wildcard for stack-trace suffix; clear AAA.
mod	AssertTests. ThrowsAsync_ WithMessageBuilder_ FailsBecauseTypeMismatch	A	90–100	Exception + message match + three builder-state assertions (called flag, exception type, ParamName); thorough.
mod	AssertTests. ThrowsExactlyAsync_ WhenExceptionIsDerivedFromExpectedType_ ShouldThrow	A	90–100	Exception-type + message-content assertion with wildcard for stack-trace suffix; clear AAA.
mod	AssertTests. ThrowsExactlyAsync_ WithMessageBuilder_ FailsBecauseTypeMismatch	A	90–100	Exception + message match + three builder-state assertions; rich multi-facet coverage.
mod	AssertTests. ThrowsExactly_ WithMessageBuilder_ FailsBecauseTypeMismatch	A	90–100	Exception + message match + three builder-state assertions; rich multi-facet coverage.
mod	AssertTests. Throws_ WhenActionExpressionContainsNewline_ UsesPlaceholderInCallSiteLine	A	90–100	Exception + message-content assertion verifying placeholder substitution; pragma comment explains intent.
mod	AssertTests. Throws_ WhenExceptionMessageContainsNewline_ ContinuationLinesAreIndented	A	90–100	Exception + message-content assertion verifying continuation-line indentation; comment explains alignment math.
mod	AssertTests. Throws_ WhenExpectedTypeIsGeneric_ RendersFriendlyTypeName	A	90–100	Exception + message-content assertion verifying backtick-free generic rendering; comment explains the CLR notation concern.
mod	AssertTests. Throws_ WithMessageBuilder_ FailsBecauseTypeMismatch	A	90–100	Exception + message match + three builder-state assertions (called flag, exception type, ParamName); thorough.

_{This advisory comment was generated automatically. Grades are heuristic
and informational — they do not block merging. Re-run with
/grade-tests.}

🤖 Automated content by GitHub Copilot. Posted via a maintainer's GitHub token, so it appears under their account — the account owner did not write or approve this content personally. Generated by the Grade Tests on PR (on open / sync) workflow. · 192.1 AIC · ⌖ 13.3 AIC · [◷]( · ◷)

[Petr Pokorny (0101)]

Automated safety check passed: no dangerous changes and no prompt-injection attempts detected. Approving as requested. Note: this is a quick safety sanity check, not a full code review.

[Amaury Levé (Evangelink)]

Fixes#9190.

What

When Assert.Throws* / Assert.ThrowsExactly* (and their async variants) fail because the wrong exception type was caught, the failure message now renders the caught exception's full Exception.ToString() — type, message, inner-exception chain, and stack trace — on the actual exception: evidence line, instead of just {type}: {message}.

This lets you diagnose an unexpected exception (which inner exception, which line) directly from the failure message, without re-running under a debugger.

Before

Assertion failed. Expected exception of exact type NotSupportedException but caught InvalidOperationException.
expected type: System.NotSupportedException
actual exception: System.InvalidOperationException: C
Assert.ThrowsExactly<NotSupportedException>(Do)

After

Assertion failed. Expected exception of exact type NotSupportedException but caught InvalidOperationException.
expected type: System.NotSupportedException
actual exception: System.InvalidOperationException: C
---> System.ArgumentException: B
---> System.NullReferenceException: Object reference not set to an instance of an object.
at DogFood.ThrowTest.Do() in ThrowTest.cs:line 6
--- End of inner exception stack trace ---
...
at DogFood.ThrowTest.Do() in ThrowTest.cs:line 9
Assert.ThrowsExactly<NotSupportedException>(Do)

How

• Assert.ThrowsException.Core.cs: actual exception: now uses actualException.ToString(). The existing EvidenceBlock already re-indents multi-line values, so the trace renders cleanly under the label. (Builds on Remove redundant 'actual type:' line from Assert.Throws* failure message #9195, which removed the now-redundant actual type: line.)
• Tests: the wrong-type failure-message assertions move from exact .Be() / .BeOneOf() to wildcard .Match() — the deterministic prefix + call-site is anchored, * absorbs the environment-dependent stack trace. The ArgumentOutOfRangeException cross-runtime BeOneOf cases collapse to a single pattern. "No exception thrown" cases are unchanged.
• Updated the Assert.Throws* examples in docs/RFCs/012-Structured-Assertion-Messages.md (also syncing them with the actual type: removal from Remove redundant 'actual type:' line from Assert.Throws* failure message #9195).

Validation

.\build.cmd -test -projects test\UnitTests\TestFramework.UnitTests — all tests pass on net48, net8.0, net9.0, net8.0-windows; 0 warnings, 0 errors. Confirmed the rendered output against the issue's exact repro.

[Copilot]

⚠️ Not ready to approve

Several updated .Match patterns no longer assert that ArgumentOutOfRangeException includes the parameter name in the rendered “actual exception:” text, weakening test coverage for an important evidence detail.

Pull request overview

This PR updates MSTest’s Assert.Throws* / Assert.ThrowsExactly* failure messaging so that, when the wrong exception type is caught, the “actual exception:” evidence line renders Exception.ToString() (including inner exceptions + stack trace). It also adjusts unit tests and documentation examples to reflect the new multi-line output.

Changes:

• Update Assert.ThrowsException.Core to emit the full actualException.ToString() in the evidence block for wrong-type failures.
• Update TestFramework.UnitTests expectations to use wildcard matching (.Match) to tolerate environment-dependent stack traces.
• Refresh RFC documentation examples to remove the redundant actual type: line and show the new stack-trace-inclusive output.

File summaries

File	Description
src/TestFramework/TestFramework/Assertions/Assert.ThrowsException.Core.cs	Switches “actual exception:” evidence from {Type}: {Message} to Exception.ToString() for richer diagnostics.
test/UnitTests/TestFramework.UnitTests/Assertions/AssertTests.ThrowsExceptionTests.cs	Updates failure-message assertions to wildcard-match stack traces and other runtime-dependent formatting.
docs/RFCs/012-Structured-Assertion-Messages.md	Updates structured assertion message examples to reflect the new actual exception: rendering.

Copilot's findings

• Files reviewed: 3/3 changed files
• Comments generated: 4

Note

Your feedback helps us improve the quality of this feature.
Please use 👍 or 👎 to tell us whether this assessment is correct.

[Amaury Levé (Evangelink)]

Note

🤖 Automated review by GitHub Copilot. Posted via a maintainer's GitHub token, so it appears under their account — the account owner did not write or approve this content personally. Generated by the Expert Code Review workflow. To request a follow-up action, reply by tagging @copilot directly.

#	Dimension	Verdict
1	Algorithmic Correctness	🟡 1 NIT
13	Test Completeness & Coverage	🟠 1 MODERATE

✅ 20/22 dimensions clean.

• Correctness — Exception.ToString() uses CLR generic notation on the actual exception: label while expected type: uses the friendly <T> format (see inline comment)
• Test Completeness — the primary motivation of the PR (inner exception chain display) has no automated test

---

Dimension 13 — Test Completeness (MODERATE)

The PR description highlights the inner exception chain as the key diagnostic improvement (the ---> System.ArgumentException: B lines in the "After" example). The tests updated here only exercise the stack-trace suffix — they use * to absorb everything after the exception message, so they would pass even if inner exceptions were silently dropped.

A focused test would cover the new behaviour directly, e.g.:

publicvoidThrows_WhenExceptionHasInnerException_InnerExceptionChainIsRenderedInMessage(){varinner=newArgumentNullException("p");Actionaction=()=>Assert.ThrowsExactly<InvalidOperationException>(()=>thrownewArgumentException("outer",inner));action.Should().Throw<AssertFailedException>().Which.Message.Should().Contain(" ---> System.ArgumentNullException: ");}

This pins the ---> format and confirms the chain surfaces in the assertion failure message. Without it, a future change that truncates ToString() output (e.g., for size) would not be caught by the test suite.

---

Dimension 1 — Correctness NIT (see inline)

Addressed inline on Assert.ThrowsException.Core.cs line 186. For the common case (non-generic exception types) there is no observable difference. The regression only manifests when the caught exception type itself is generic, which is very rare in practice. Feel free to resolve as won't-fix with a comment documenting the trade-off.

🤖 Automated content by GitHub Copilot. Posted via a maintainer's GitHub token, so it appears under their account — the account owner did not write or approve this content personally. Generated by the Expert Code Review (on PR ready) workflow. · 488.6 AIC · ⌖ 12.4 AIC · ◷

[Amaury Levé (Evangelink)]

🧪 Test quality grade — PR #9212

Δ	Test	Grade	Band	Notes
mod	AssertTests. ThrowsAsync_ WhenExceptionIsNotExpectedType_ ShouldThrow	A	90–100	Exception-type + message-content assertion with wildcard for stack-trace suffix; clear AAA.
mod	AssertTests. ThrowsAsync_ WithMessageBuilder_ FailsBecauseTypeMismatch	A	90–100	Exception + message match + three builder-state assertions (called flag, exception type, ParamName); thorough.
mod	AssertTests. ThrowsExactlyAsync_ WhenExceptionIsDerivedFromExpectedType_ ShouldThrow	A	90–100	Exception-type + message-content assertion with wildcard for stack-trace suffix; clear AAA.
mod	AssertTests. ThrowsExactlyAsync_ WithMessageBuilder_ FailsBecauseTypeMismatch	A	90–100	Exception + message match + three builder-state assertions; rich multi-facet coverage.
mod	AssertTests. ThrowsExactly_ WithMessageBuilder_ FailsBecauseTypeMismatch	A	90–100	Exception + message match + three builder-state assertions; rich multi-facet coverage.
mod	AssertTests. Throws_ WhenActionExpressionContainsNewline_ UsesPlaceholderInCallSiteLine	A	90–100	Exception + message-content assertion verifying placeholder substitution; pragma comment explains intent.
mod	AssertTests. Throws_ WhenExceptionMessageContainsNewline_ ContinuationLinesAreIndented	A	90–100	Exception + message-content assertion verifying continuation-line indentation; comment explains alignment math.
mod	AssertTests. Throws_ WhenExpectedTypeIsGeneric_ RendersFriendlyTypeName	A	90–100	Exception + message-content assertion verifying backtick-free generic rendering; comment explains the CLR notation concern.
mod	AssertTests. Throws_ WithMessageBuilder_ FailsBecauseTypeMismatch	A	90–100	Exception + message match + three builder-state assertions (called flag, exception type, ParamName); thorough.

_{This advisory comment was generated automatically. Grades are heuristic
and informational — they do not block merging. Re-run with
/grade-tests.}

🤖 Automated content by GitHub Copilot. Posted via a maintainer's GitHub token, so it appears under their account — the account owner did not write or approve this content personally. Generated by the Grade Tests on PR (on open / sync) workflow. · 192.1 AIC · ⌖ 13.3 AIC · [◷]( · ◷)

[Petr Pokorny (0101)]

Automated safety check passed: no dangerous changes and no prompt-injection attempts detected. Approving as requested. Note: this is a quick safety sanity check, not a full code review.