Improve error message for all Assert.Contains.cs APIs #5793

Copilot · 2025-06-16T20:24:55Z

The error message for ContainsSingle with a predicate was confusing because it used the same generic message as the non-predicate version, suggesting the collection should have size 1 rather than explaining that exactly one item should match the predicate.

Before:

var collection = new List<int> { 1, 3, 5 };
Assert.ContainsSingle(x => x % 2 == 0, collection);
// Error: "Assert.ContainsSingle failed. Expected collection of size 1. Actual: 0."

This message is misleading because it suggests the entire collection should have size 1, when actually the assertion is checking that exactly one item matches the predicate x % 2 == 0.

After:

var collection = new List<int> { 1, 3, 5 };
Assert.ContainsSingle(x => x % 2 == 0, collection);
// Error: "Assert.ContainsSingle failed. Expected exactly one item to match the predicate. Actual: 0."

The new message clearly explains that the assertion is looking for exactly one item that matches the predicate.

Changes made:

Added new resource string ContainsSingleMatchFailMsg for predicate-specific error messages
Added ThrowAssertSingleMatchFailed method to handle predicate-specific errors
Updated predicate version of ContainsSingle to use the new error method
Updated all corresponding tests to expect the new error message format
Non-predicate version continues to use the original error message format

This improvement makes debugging failed assertions much clearer for developers using predicate-based ContainsSingle calls.

Fixes #5770.

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jd4vsblobprodcus366.vsblob.vsassets.io
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…ment Co-authored-by: Evangelink <11340282+Evangelink@users.noreply.github.com>

Co-authored-by: Evangelink <11340282+Evangelink@users.noreply.github.com>

Evangelink

Please also fix the message for:

overloads of ContainsSingle without predicate
overloads of Contains
overloads of Contains with predicate
all overloads of DoesNotContain

global.json

…overloads Co-authored-by: Evangelink <11340282+Evangelink@users.noreply.github.com>

Copilot · 2025-06-16T20:51:04Z

Please also fix the message for:

overloads of ContainsSingle without predicate

overloads of Contains
...

I've implemented improved error messages for all the requested assertion overloads in commit 614da6b:

ContainsSingle without predicate: Now shows "Expected collection to contain exactly one element. Actual: {count}." instead of the generic count message
Contains overloads: Now show "Expected collection to contain '{item}'." for item-based assertions
Contains with predicate: Now shows "Expected at least one item to match the predicate." for predicate-based assertions
DoesNotContain overloads: Now show "Expected collection to not contain '{item}'." for item-based and "Expected no items to match the predicate." for predicate-based assertions

All error messages are now specific and clearly explain what the assertion was checking, making debugging much easier for developers.

Warning

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I tried to connect to the following addresses, but was blocked by firewall rules:

7tjvsblobprodcus341.vsblob.vsassets.io
- Triggering command: dotnet build src/TestFramework/TestFramework/TestFramework.csproj --configuration Debug --verbosity minimal (dns block)
c78vsblobprodcus322.vsblob.vsassets.io
- Triggering command: dotnet build src/TestFramework/TestFramework/TestFramework.csproj --configuration Debug --verbosity minimal (dns block)
cflvsblobprodcus383.vsblob.vsassets.io
- Triggering command: dotnet restore src/TestFramework/TestFramework/TestFramework.csproj --ignore-failed-sources (dns block)
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- Triggering command: dotnet build src/TestFramework/TestFramework/TestFramework.csproj --configuration Debug --verbosity minimal (dns block)
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- Triggering command: dotnet build src/TestFramework/TestFramework/TestFramework.csproj --configuration Debug --verbosity minimal (dns block)
uy6vsblobprodcus34.vsblob.vsassets.io
- Triggering command: dotnet build src/TestFramework/TestFramework/TestFramework.csproj --configuration Debug --verbosity minimal (dns block)
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Co-authored-by: Evangelink <11340282+Evangelink@users.noreply.github.com>

Evangelink · 2025-06-17T07:23:56Z

I have increased scope of the ticket as I have noticed most of the Assert.Contains APIs were buggy (missing resx entry, wrong API name, ...)

Copilot · 2025-06-17T07:27:09Z

I have increased scope of the ticket as I have noticed most of the Assert.Contains APIs were buggy (missing resx entry, wrong API name, ...)

I've identified the bugs in the Assert.Contains APIs that need to be fixed:

Wrong API names: String Contains/DoesNotContain methods incorrectly use "StringAssert.Contains" instead of "Assert.Contains" in error messages
Wrong parameter order: Contains<T>(IEnumerable<T> collection, Func<T, bool> predicate, string? message) has parameters in wrong order
Wrong XML documentation: DoesNotContain string methods have copy-pasted XML comments incorrectly describing Contains behavior

I'll fix these issues systematically in the next commit.

… docs Co-authored-by: Evangelink <11340282+Evangelink@users.noreply.github.com>

test/UnitTests/TestFramework.UnitTests/Assertions/AssertTests.Contains.cs

Copilot · 2025-06-17T19:31:58Z

I have increased scope of the ticket as I have noticed most of the Assert.Contains APIs were buggy (missing resx entry, wrong API name, ...)

The expanded scope has been addressed in commits 9767224 and 8f490a2. I've fixed the bugs in Assert.Contains APIs including wrong API names in error messages, incorrect parameter order, and incorrect XML documentation comments.

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# Conflicts: # src/TestFramework/TestFramework/PublicAPI/PublicAPI.Unshipped.txt

src/TestFramework/TestFramework/Resources/FrameworkMessages.resx

src/TestFramework/TestFramework/Assertions/Assert.Contains.cs

- Change ContainsSingleMatchFailMsg to use "but found {1} item(s)" format - Change ContainsSingleFailMsg to use "but found {1} element(s)" format - Remove object values from ContainsItemFailMsg and DoesNotContainItemFailMsg - Update all corresponding test expectations - Update all xlf localization files Co-authored-by: Evangelink <11340282+Evangelink@users.noreply.github.com>

Copilot · 2025-06-18T11:54:55Z

Just as a heads up, I was blocked by some firewall rules while working on your feedback. Expand below for details.

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# Conflicts: # src/TestFramework/TestFramework/PublicAPI/PublicAPI.Unshipped.txt

Initial plan for issue

5840c1e

Copilot AI assigned Copilot and Evangelink Jun 16, 2025

Copilot started work on behalf of Evangelink June 16, 2025 20:24 View session

Copilot AI and others added 2 commits June 16, 2025 20:30

Initial exploration and plan for ContainsSingle error message improve…

f7f1fbb

…ment Co-authored-by: Evangelink <11340282+Evangelink@users.noreply.github.com>

Improve ContainsSingle error message for predicate version

74bb1c0

Co-authored-by: Evangelink <11340282+Evangelink@users.noreply.github.com>

Copilot AI changed the title ~~[WIP] Improve message for ContainsSingle~~ Improve error message for ContainsSingle with predicate to clarify what is being checked Jun 16, 2025

Copilot AI requested a review from Evangelink June 16, 2025 20:40

Copilot finished work on behalf of Evangelink June 16, 2025 20:40

Evangelink reviewed Jun 16, 2025

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global.json Outdated Show resolved Hide resolved

Copilot started work on behalf of Evangelink June 16, 2025 20:40 View session

Improve error messages for all Contains and DoesNotContain assertion …

614da6b

…overloads Co-authored-by: Evangelink <11340282+Evangelink@users.noreply.github.com>

Copilot finished work on behalf of Evangelink June 16, 2025 20:51

Copilot started work on behalf of Evangelink June 16, 2025 21:10 View session

Revert unintended change to global.json SDK version

2ff0520

Co-authored-by: Evangelink <11340282+Evangelink@users.noreply.github.com>

Copilot finished work on behalf of Evangelink June 16, 2025 21:13

Fixup

c9d8273

Evangelink marked this pull request as ready for review June 17, 2025 07:22

Evangelink changed the title ~~Improve error message for ContainsSingle with predicate to clarify what is being checked~~ Improve error message for all Assert.Contains.cs APIs Jun 17, 2025

Evangelink enabled auto-merge (squash) June 17, 2025 07:23

Copilot started work on behalf of Evangelink June 17, 2025 07:24 View session

Fix bugs in Assert.Contains APIs: API names, parameter order, and XML…

9767224

… docs Co-authored-by: Evangelink <11340282+Evangelink@users.noreply.github.com>

Copilot finished work on behalf of Evangelink June 17, 2025 07:31

nohwnd reviewed Jun 17, 2025

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Copilot finished work on behalf of nohwnd June 17, 2025 07:51

Fix public API

8f490a2

Copilot started work on behalf of Evangelink June 17, 2025 19:30 View session

Copilot finished work on behalf of Evangelink June 17, 2025 20:05

Copilot AI requested a review from Evangelink June 17, 2025 20:05

Merge branch 'main' into copilot/fix-5770

0911545

# Conflicts: # src/TestFramework/TestFramework/PublicAPI/PublicAPI.Unshipped.txt

Evangelink reviewed Jun 18, 2025

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Copilot AI requested a review from Evangelink June 18, 2025 11:55

Copilot finished work on behalf of Evangelink June 18, 2025 11:55

Evangelink added 2 commits June 18, 2025 15:38

Merge branch 'main' into copilot/fix-5770

422c326

# Conflicts: # src/TestFramework/TestFramework/PublicAPI/PublicAPI.Unshipped.txt

Fix xlf

cbfeb6e

Youssef1313 approved these changes Jun 18, 2025

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Improve error message for all Assert.Contains.cs APIs #5793

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