FluentAssertionsToShouldlyAnalyzer

A basic Roslyn analyzer to migrate from FluentAssertions to Shouldly.

Context

With the recent license change of FluentAssertions to a commercial model, many developers are seeking for alternatives. Shouldly offers a clean and expressive syntax for assertions, pretty muche the same as FA.

This analyzer aims to ease the migration process by identifying usages of FluentAssertions and suggesting equivalent Shouldly assertions.

Features

• Detects FluentAssertions usages in C# code and reports diagnostics with messages suggesting to Migrate to Shouldly.
• (Planned) Provides automatic code fixes to apply Shouldly syntax.

Installation

1. Add the NuGet package (coming soon) to your test project.
2. Build your project to see diagnostics.
3. Apply code fixes (when implemented).

Supported Assertions

Currently, based on this guide from the Shouldly repo, the analyzer detects and suggests replacements for :

FluentAssertions	Shouldly
result.Should().Be(expected);	result.ShouldBe(expected);
result.Should().NotBe(unexpected);	result.ShouldNotBe(unexpected);
result.Should().BeNull();	result.ShouldBeNull();
result.Should().NotBeNull();	result.ShouldNotBeNull();
result.Should().BeTrue();	result.ShouldBeTrue();
result.Should().BeFalse();	result.ShouldBeFalse();
result.Should().BeSameAs(expected);	result.ShouldBeSameAs(expected);
result.Should().NotBeSameAs(unexpected);	result.ShouldNotBeSameAs(unexpected);
result.Should().BeOfType();	result.ShouldBeOfType();
result.Should().NotBeOfType();	result.ShouldNotBeOfType();
result.Should().BeGreaterThan(value);	result.ShouldBeGreaterThan(value);
result.Should().BeGreaterThanOrEqualTo(value);	result.ShouldBeGreaterThanOrEqualTo(value);
result.Should().BeLessThan(value);	result.ShouldBeLessThan(value);
result.Should().BeLessThanOrEqualTo(value);	result.ShouldBeLessThanOrEqualTo(value);
result.Should().BePositive();	result.ShouldBePositive();
result.Should().BeNegative();	result.ShouldBeNegative();
result.Should().BeInRange(low, high);	result.ShouldBeInRange(low, high);
result.Should().NotBeInRange(low, high);	result.ShouldNotBeInRange(low, high);
collection.Should().Contain(item);	collection.ShouldContain(item);
collection.Should().NotContain(item);	collection.ShouldNotContain(item);
collection.Should().BeEmpty();	collection.ShouldBeEmpty();
collection.Should().NotBeEmpty();	collection.ShouldNotBeEmpty();
collection.Should().HaveCount(count);	collection.Count.ShouldBe(count);
collection.Should().HaveCountGreaterThan(value);	collection.Count.ShouldBeGreaterThan(value);
collection.Should().HaveCountLessThan(value);	collection.Count.ShouldBeLessThan(value);
collection.Should().AllBeAssignableTo();	collection.ShouldAllBeAssignableTo();
collection.Should().OnlyHaveUniqueItems();	collection.ShouldAllBeUnique();
dictionary.Should().ContainKey(key);	dictionary.ShouldContainKey(key);
dictionary.Should().NotContainKey(key);	dictionary.ShouldNotContainKey(key);
dictionary.Should().ContainValue(value);	dictionary.ShouldContainValue(value);
dictionary.Should().NotContainValue(value);	dictionary.ShouldNotContainValue(value);
action.Should().Throw();	action.ShouldThrow();
action.Should().NotThrow();	action.ShouldNotThrow();
action.Should().NotThrow();	action.ShouldNotThrow();
action.Should().ThrowExactly();	action.ShouldThrowExactly();
action.Should().Throw().WithMessage("message");	action.ShouldThrow().Message.ShouldBe("message");

TODO

• Implement code fix provider for automatic assertion replacement.
• Expand support to other common FluentAssertions methods.
• Add test coverage and CI integration.

Contribution

Contributions are welcome! If you find a bug/issue/discussion, Feel free to open issues or pull requests.

License

This project is licensed under the MIT License.

References

• Code analysis using .NET compiler platform (Roslyn) analyzers - Visual Studio (Windows) | Microsoft Learn
• Tutorial: Write your first analyzer and code fix - C# | Microsoft Learn
• https://github.com/agoda-com/Shouldly.FromAssert
• Onboarding guide for FluentAssertions · Issue #1034 · shouldly/shouldly
• fluentassertions/fluentassertions

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Thanks to

• The Shouldly Team for making one of the best assertion library for .NET projects. 👏🏽
• The AWesome Roslyn Team for making analyzer creation feel like a peace of cake.
• The Shouldly.FromAssert repo for the idea. :)
• All the contributors.