Improve rendering of exception messages when using WithMessage by dennisdoomen · Pull Request #3039 · fluentassertions/fluentassertions

dennisdoomen · 2025-03-13T15:04:52Z

In a test like When_one_of_the_types_does_not_match_the_generic_type_it_should_throw_with_a_clear_explanation, a multi-line exception message like this

Expected exception message to match the equivalent of "Expected type to be "System.Int33" because they are of different type, but found "[System.Int32, System.String, System.Int32]".", but "Expected type to be "System.Int32" because they are of different type, but found "[System.Int32, System.String, System.Int32]"." does not.

after this PR, they will be rendered as

Expected exception message to match the equivalent of

    "Expected type to be "System.Int33" because they are of different type, but found "[System.Int32, System.String, System.Int32]".",

but

    "Expected type to be "System.Int32" because they are of different type, but found "[System.Int32, System.String, System.Int32]"."

does not.

github-actions · 2025-03-13T15:07:05Z

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coveralls · 2025-03-26T00:24:55Z

Pull Request Test Coverage Report for Build 14133594137

Details

68 of 71 (95.77%) changed or added relevant lines in 9 files are covered.
No unchanged relevant lines lost coverage.
Overall coverage decreased (-0.03%) to 97.358%

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
Src/FluentAssertions/Primitives/StringContainsStrategy.cs	1	4	25.0%

Totals
Change from base Build 14090391235:	-0.03%
Covered Lines:	12442
Relevant Lines:	12637

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Pull Request Overview

This PR improves the rendering of exception messages by reformatting multi-line messages and refactoring string comparison and validation methods. Key changes include updating tests to assert multi‐line formatting, renaming and consolidating validation methods across multiple string comparison strategies, and adjusting the trimming behavior in the formatting component.

Reviewed Changes

Copilot reviewed 11 out of 12 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
Tests/FluentAssertions.Specs/Exceptions/OuterExceptionSpecs.cs	Added tests to verify multi‐line, long, and short exception message rendering.
Src/FluentAssertions/Specialized/ExceptionAssertions.cs	Refactored exception message assertion logic for clearer output.
Src/FluentAssertions/Primitives/StringWildcardMatchingStrategy.cs	Renamed methods and updated formatting for multi‐line messages.
Src/FluentAssertions/Primitives/StringValidatorSupportingNull.cs	Updated to call the new AssertForEquality method.
Src/FluentAssertions/Primitives/StringValidator.cs	Replaced null validation with a call to AssertNeitherIsNull for better consistency.
Src/FluentAssertions/Primitives/StringStartStrategy.cs	Renamed mismatch validation method and added null checks.
Src/FluentAssertions/Primitives/StringEqualityStrategy.cs	Renamed methods and updated error message formatting.
Src/FluentAssertions/Primitives/StringEndStrategy.cs	Modified error messages and integrated a new null check method.
Src/FluentAssertions/Primitives/StringContainsStrategy.cs	Renamed methods and updated error message parameter ordering.
Src/FluentAssertions/Primitives/IStringComparisonStrategy.cs	Updated the interface to match the new method names.
Src/FluentAssertions/Formatting/Line.cs	Adjusted trimming behavior in ToString to explicitly remove trailing spaces.

Files not reviewed (1)

Tests/FluentAssertions.Specs/FluentAssertions.Specs.csproj: Language not supported

Comments suppressed due to low confidence (1)

Src/FluentAssertions/Primitives/StringContainsStrategy.cs:25

[nitpick] Verify that the parameter order in the error message is intentional; currently, 'subject' is passed as the first parameter and 'expected' as the second, which might lead to confusion compared to similar strategies.

                $"Expected {context:string} {0} to contain the equivalent of {1} {expectedOccurrence}{reason}, but found it {actual.Times()}."

Src/FluentAssertions/Formatting/Line.cs

Tests/FluentAssertions.Specs/Exceptions/OuterExceptionSpecs.cs

Src/FluentAssertions/Primitives/StringWildcardMatchingStrategy.cs

dennisdoomen · 2025-03-28T16:35:39Z

@jnyrup did you not approve or reject the PR on purpose?

Updated [FluentAssertions](https://github.com/fluentassertions/fluentassertions) from 8.0.0 to 8.8.0. <details> <summary>Release notes</summary> _Sourced from [FluentAssertions's releases](https://github.com/fluentassertions/fluentassertions/releases)._ ## 8.8.0  ## What's Changed ### New features * Add support for MSTest4 by @jnyrup in fluentassertions/fluentassertions#3111 ### Improvements * Allow WithoutMessage when using Should().Throw() and ThrowAsync() by @dennisdoomen in fluentassertions/fluentassertions#3100 * Improve reporting of the differences between long strings by @dennisdoomen in fluentassertions/fluentassertions#3101 * Allow customizing the equivalency behavior for BeXmlSerializable by @logiclrd in fluentassertions/fluentassertions#3107 ### Documentation * Add docs for `config` parameter by @jnyrup in fluentassertions/fluentassertions#3104 ### Others * Refreshed readme by @dennisdoomen in fluentassertions/fluentassertions#3106 * Merge hotfix 8.7.1 back to main by @dennisdoomen in fluentassertions/fluentassertions#3109 * Fix release notes by @jnyrup in fluentassertions/fluentassertions#3112 * Bump github/codeql-action from 3 to 4 by @dependabot[bot] in fluentassertions/fluentassertions#3113 **Full Changelog**: fluentassertions/fluentassertions@8.7.1...8.8.0 ## 8.7.1  ## What's Changed ### Others * JSON assertions did not properly handle floats, doubles and unsigned … by @dennisdoomen in fluentassertions/fluentassertions#3105 * Fixed ambiguity when using Should on a JsonNode derived class ... by @JSkimming in fluentassertions/fluentassertions#3102 **Full Changelog**: fluentassertions/fluentassertions@8.7.0...8.7.1 ## 8.7.0  ## What's Changed ### New features * Added System.Text.Json assertion APIs and BeEquivalentTo support by @dennisdoomen in fluentassertions/fluentassertions#3094 ### Others * Address a bunch of Qodana issues by @dennisdoomen in fluentassertions/fluentassertions#3082 * Bump actions/checkout from 4 to 5 by @dependabot[bot] in fluentassertions/fluentassertions#3085 * Bump JetBrains/qodana-action from 2025.1 to 2025.2 by @dependabot[bot] in fluentassertions/fluentassertions#3086 * Bump actions/download-artifact from 4 to 5 by @dependabot[bot] in fluentassertions/fluentassertions#3087 * Bump cspell from 9.2.0 to 9.2.1 by @dependabot[bot] in fluentassertions/fluentassertions#3090 * Bump actions/setup-dotnet from 4 to 5 by @dependabot[bot] in fluentassertions/fluentassertions#3092 * Add lock file for nuget packages by @jnyrup in fluentassertions/fluentassertions#3084 * Set `DisableImplicitNuGetFallbackFolder` by @jnyrup in fluentassertions/fluentassertions#3095 * Bump Nugets by @jnyrup in fluentassertions/fluentassertions#3096 * Revert package locking by @jnyrup in fluentassertions/fluentassertions#3098 * Clean-up tests related to exceptions by @dennisdoomen in fluentassertions/fluentassertions#3099 **Full Changelog**: fluentassertions/fluentassertions@8.6.0...8.7.0 ## 8.6.0  ## What's Changed ### Improvements * Add support for inline assertions using `Value.ThatMatches` and `Value.ThatSatisfies` by @dennisdoomen in fluentassertions/fluentassertions#3076 ### Others * Remove Microsoft.SourceLink.GitHub by @SimonCropp in fluentassertions/fluentassertions#3072 * Bump cspell from 9.1.3 to 9.1.5 by @dependabot[bot] in fluentassertions/fluentassertions#3073 * Added PackageGuard to the build pipeline by @dennisdoomen in fluentassertions/fluentassertions#3075 * Bump cspell from 9.1.5 to 9.2.0 by @dependabot[bot] in fluentassertions/fluentassertions#3077 * Remove dependencies on Bogus by @jnyrup in fluentassertions/fluentassertions#3080 * Update nuget packages by @jnyrup in fluentassertions/fluentassertions#3081 * Follow-up to #3076 by @jnyrup in fluentassertions/fluentassertions#3079 * Documentation and typo fixes by @jnyrup in fluentassertions/fluentassertions#3078 ## New Contributors * @SimonCropp made their first contribution in fluentassertions/fluentassertions#3072 **Full Changelog**: fluentassertions/fluentassertions@8.5.0...8.6.0 ## 8.5.0  ## What's Changed ### New features * Extended BeEquivalentTo with support for checking the type of the properties by @dennisdoomen in fluentassertions/fluentassertions#3066 ### Fixes * Ensured WithTracing is safe when used with BeEquivalentTo globally by @dennisdoomen in fluentassertions/fluentassertions#3067 ### Others * Revisit the .editorconfig rules by @dennisdoomen in fluentassertions/fluentassertions#3063 * Bump cspell from 9.1.1 to 9.1.2 by @dependabot[bot] in fluentassertions/fluentassertions#3068 * Use .NET 9 SDK by @jnyrup in fluentassertions/fluentassertions#3069 * Bump cspell from 9.1.2 to 9.1.3 by @dependabot[bot] in fluentassertions/fluentassertions#3071 **Full Changelog**: fluentassertions/fluentassertions@8.4.0...8.5.0 ## 8.4.0  ## What's Changed ### Improvements * Allow excluding properties by name anywhere in the graph by @dennisdoomen in fluentassertions/fluentassertions#3062 * Added Should().Throw(), ThrowAsync() and ThrowWithinAsync() flavors that don’t require a specific exception type by @Xceed-DelvaJB in fluentassertions/fluentassertions#3059 ### Others * Bump cspell from 9.0.1 to 9.0.2 by @dependabot in fluentassertions/fluentassertions#3050 * Bump JetBrains/qodana-action from 2024.2 to 2025.1 by @dependabot in fluentassertions/fluentassertions#3044 * Fix qodana warnings by @jnyrup in fluentassertions/fluentassertions#3053 * Add contributor grant by @dennisdoomen in fluentassertions/fluentassertions#3055 * Bump cspell from 9.0.2 to 9.1.1 by @dependabot in fluentassertions/fluentassertions#3058 ## New Contributors * @Xceed-DelvaJB made their first contribution in fluentassertions/fluentassertions#3059 **Full Changelog**: fluentassertions/fluentassertions@8.3.0...8.4.0 ## 8.3.0  ## What's Changed ### Improvements * Improve rendering of exception messages when using WithMessage by @dennisdoomen in fluentassertions/fluentassertions#3039 * Clarify the date/time type when comparing dates, times and combinations of those by @dennisdoomen in fluentassertions/fluentassertions#3049 ### Others * Bump cspell from 8.17.5 to 8.18.1 by @dependabot in fluentassertions/fluentassertions#3041 * Bump cspell from 8.18.1 to 8.19.2 by @dependabot in fluentassertions/fluentassertions#3042 * Bump cspell from 8.19.2 to 8.19.3 by @dependabot in fluentassertions/fluentassertions#3043 * Bump cspell from 8.19.3 to 9.0.0 by @dependabot in fluentassertions/fluentassertions#3045 * Bump cspell from 9.0.0 to 9.0.1 by @dependabot in fluentassertions/fluentassertions#3046 * Fix links to test suites in bug report template by @robvanuden in fluentassertions/fluentassertions#3047 **Full Changelog**: fluentassertions/fluentassertions@8.2.0...8.3.0 ## 8.2.0  ## What's Changed ### Improvements * Optimize various string operations by @jnyrup in fluentassertions/fluentassertions#3037 * Reworked formatting and support multi-dimensional arrays. by @dennisdoomen in fluentassertions/fluentassertions#3009 ### Fixes * Restore `StringSyntax` annotations by @jnyrup in fluentassertions/fluentassertions#3033 * Regex fixups by @jnyrup in fluentassertions/fluentassertions#3034 * Handle missing caller identifier by @jnyrup in fluentassertions/fluentassertions#3036 ### Others * Bump cspell from 8.17.3 to 8.17.5 by @dependabot in fluentassertions/fluentassertions#3035 **Full Changelog**: fluentassertions/fluentassertions@8.1.1...8.2.0 ## 8.1.1  ## What's Changed ### Fixes * Fix a formatting exception when {} is used as a dictionary key. by @dennisdoomen in fluentassertions/fluentassertions#3029 * Removed the PS script that opens the FA website because it misbehaves. by @dennisdoomen in fluentassertions/fluentassertions#3030 **Full Changelog**: fluentassertions/fluentassertions@8.1.0...8.1.1 ## 8.1.0  ## What's Changed ### Improvements * Add [NotNull] attribute on the Should() method for object assertions by @0xced in fluentassertions/fluentassertions#2987 * Improves the subject identification for chained assertions and those that use Which by @dennisdoomen in fluentassertions/fluentassertions#3000 ### Fixes * Fixed a regression in which CompleteWithinAsync treated a canceled task as an exception by @dennisdoomen in fluentassertions/fluentassertions#2853 ### Documentation * Reconnected the new license to the history of the old license by @dennisdoomen in fluentassertions/fluentassertions#2985 * Removed an incorrect date/time example from the docs by @dennisdoomen in fluentassertions/fluentassertions#2989 ### Others * Make sure developers don't accidentally update to v8 without understanding the new license by @dennisdoomen in fluentassertions/fluentassertions#2988 * Bump Microsoft.Testing.Extensions.TrxReport from 1.5.1 to 1.5.3 by @dependabot in fluentassertions/fluentassertions#2993 * Bump TUnit from 0.6.154 to 0.7.24 by @dependabot in fluentassertions/fluentassertions#2992 * Bump the mstest group with 2 updates by @dependabot in fluentassertions/fluentassertions#2991 * Backport updates to pipelines by @jnyrup in fluentassertions/fluentassertions#3001 * Bump cspell from 8.17.2 to 8.17.3 by @dependabot in fluentassertions/fluentassertions#3005 * Bump Roslynator.Analyzers from 4.12.10 to 4.12.11 by @dependabot in fluentassertions/fluentassertions#3004 * Bump TUnit from 0.7.24 to 0.10.6 by @dependabot in fluentassertions/fluentassertions#3002 * Upmerge from v7 by @dennisdoomen in fluentassertions/fluentassertions#3006 * Renamed CallerStatementBuilder to StatementParser by @dennisdoomen in fluentassertions/fluentassertions#3007 * Bump Meziantou.Analyzer and Microsoft.NETFramework.ReferenceAssemblies by @dependabot in fluentassertions/fluentassertions#3014 * Bump Microsoft.NET.Test.Sdk, Microsoft.NETFramework.ReferenceAssemblies and Newtonsoft.Json by @dependabot in fluentassertions/fluentassertions#3013 * Bump Microsoft.NETFramework.ReferenceAssemblies and Roslynator.Analyzers by @dependabot in fluentassertions/fluentassertions#3012 * Bump the xunit group with 3 updates by @dependabot in fluentassertions/fluentassertions#3010 * Adjust dependencies by @jnyrup in fluentassertions/fluentassertions#3015 * Bump NUnit3TestAdapter from 4.6.0 to 5.0.0 in the nunit group by @dependabot in fluentassertions/fluentassertions#3011 * Fixed typo in introduction page by @tealamore in fluentassertions/fluentassertions#3019 * Bump Verify.Xunit from 28.10.1 to 28.11.0 in the xunit group by @dependabot in fluentassertions/fluentassertions#3022 * Bump TUnit from 0.10.6 to 0.13.3 by @dependabot in fluentassertions/fluentassertions#3026 * Bump Microsoft.Testing.Extensions.CodeCoverage from 17.13.1 to 17.14.1 by @dependabot in fluentassertions/fluentassertions#3024 * Bump the mstest group with 2 updates by @dependabot in fluentassertions/fluentassertions#3023 * Bump Microsoft.NETFramework.ReferenceAssemblies, System.Collections.Immutable and System.Reflection.Metadata by @dependabot in fluentassertions/fluentassertions#3025 * Upmerge from v7 by @jnyrup in fluentassertions/fluentassertions#3028 * Fixed a regression in which CompleteWithinAsync treated a canceled ta… by @dennisdoomen in fluentassertions/fluentassertions#3027 ## New Contributors * @tealamore made their first contribution in fluentassertions/fluentassertions#3019 **Full Changelog**: fluentassertions/fluentassertions@8.0.1...8.1.0 ## 8.0.1  ## What's Changed ### Improvements * Provide a toggle to suppress the soft warning about commercial use by @dennisdoomen in fluentassertions/fluentassertions#2984 ### Others * Update docs to make license change more clear by @jnyrup in fluentassertions/fluentassertions#2953 * Bump all dependencies by @dennisdoomen in fluentassertions/fluentassertions#2962 * Bump System.Collections.Immutable and System.Reflection.Metadata by @dependabot in fluentassertions/fluentassertions#2969 * Bump SharpCompress from 0.38.0 to 0.39.0 by @dependabot in fluentassertions/fluentassertions#2968 * Bump the nuke group with 2 updates by @dependabot in fluentassertions/fluentassertions#2967 * Bump Verify.Xunit from 28.8.1 to 28.9.0 in the xunit group by @dependabot in fluentassertions/fluentassertions#2965 * Bump the mstest group with 2 updates by @dependabot in fluentassertions/fluentassertions#2966 * Bump cspell from 8.17.1 to 8.17.2 by @dependabot in fluentassertions/fluentassertions#2964 * Discard backported changes from 7 by @dennisdoomen in fluentassertions/fluentassertions#2974 * Various textual and styling fixes as well as some clarification of v7 and v8. by @dennisdoomen in fluentassertions/fluentassertions#2978 * Bump Xunit.StaFact from 1.1.11 to 1.2.69 in the xunit group by @dependabot in fluentassertions/fluentassertions#2979 * Bump TUnit from 0.6.33 to 0.6.154 by @dependabot in fluentassertions/fluentassertions#2980 * Bump Reflectify from 1.4.0 to 1.5.0 by @dependabot in fluentassertions/fluentassertions#2981 * Bump System.Formats.Asn1 from 9.0.0 to 9.0.1 by @dependabot in fluentassertions/fluentassertions#2983 * Bump coverlet.collector from 6.0.3 to 6.0.4 by @dependabot in fluentassertions/fluentassertions#2982 **Full Changelog**: fluentassertions/fluentassertions@8.0.0...8.0.1 Commits viewable in [compare view](fluentassertions/fluentassertions@8.0.0...8.8.0). </details> [![Dependabot compatibility score](https://dependabot-badges.githubapp.com/badges/compatibility_score?dependency-name=FluentAssertions&package-manager=nuget&previous-version=8.0.0&new-version=8.8.0)](https://docs.github.com/en/github/managing-security-vulnerabilities/about-dependabot-security-updates#about-compatibility-scores) Dependabot will resolve any conflicts with this PR as long as you don't alter it yourself. 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dennisdoomen added the enhancement label Mar 13, 2025

dennisdoomen force-pushed the improve-exception-messages branch 8 times, most recently from a06ba55 to 9a6ee29 Compare March 20, 2025 19:54

dennisdoomen force-pushed the improve-exception-messages branch 3 times, most recently from 187131b to e02714b Compare March 25, 2025 23:52

dennisdoomen marked this pull request as ready for review March 25, 2025 23:53

dennisdoomen added this to the 8.3.0 milestone Mar 25, 2025

dennisdoomen requested review from Copilot and jnyrup March 26, 2025 16:00

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Improve rendering of exception messages when using WithMessage

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dennisdoomen force-pushed the improve-exception-messages branch from e02714b to 14ae9cc Compare March 28, 2025 16:34

jnyrup approved these changes Mar 28, 2025

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dennisdoomen merged commit 34e1a87 into fluentassertions:main Mar 28, 2025
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dennisdoomen deleted the improve-exception-messages branch March 28, 2025 20:29

dennisdoomen mentioned this pull request May 16, 2025

Improve formatting of exception message failures #2731

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Improve rendering of exception messages when using WithMessage #3039

Improve rendering of exception messages when using WithMessage #3039
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