RoslynNUnitLight

A lightweight framework for writing unit tests for Roslyn diagnostic analyzers, code fixes and refactorings using NUnit.

Quick Start

1. Install the RoslynNUnitLight.NetStandard package from NuGet into your project.

2. Create a new class that inherits from one of the provided *TestFixture classes that matches what are going to test.

   • DiagnosticAnalyzer = AnalyzerTestFixture
   • CodeFixProvider = CodeFixTestFixture
   • CodeRefactoringProvider = CodeRefactoringTestFixture

3. Override the LanguageName property and return the appropriate value from Microsoft.CodeAnalysis.LanguageNames, depending on what language your tests will target.

4. Override the CreateAnalyzer or CreateProvider method and return an instance of your analyzer or provider.

5. Write tests!

Writing Unit Tests

RoslynNUnitLight accepts strings that are marked up with [| and |] to identify a particular span. This could represent the span of an expected diagnostic or the text selection before a refactoring is applied.

Example: Test presence of a diagnostic

[Test]
public void AutoPropDeclaredAndUsedInConstructor()
{
    const string code = @"
class C
{
	public bool MyProperty { get; [|private set;|] }
	public C(bool f)
	{
		MyProperty = f;
	}
}";

    HasDiagnostic(code, DiagnosticIds.UseGetterOnlyAutoProperty);
}

Example: Test absence of a diagnostic

[Test]
public void AutoPropAlreadyReadonly()
{
    const string code = @"
class C
{
    public bool MyProperty { get; }
    public C(bool f)
    {
        MyProperty = f;
    }
}";

    NoDiagnostic(code, DiagnosticIds.UseGetterOnlyAutoProperty);
}

Example: Test code fix behavior

[Test]
public void TestSimpleProperty()
{
    const string markupCode = @"
class C
{
    public bool P1 { get; [|private set;|] }
}";

    const string expected = @"
class C
{
    public bool P1 { get; }
}";

    TestCodeFix(markupCode, expected, DiagnosticDescriptors.UseGetterOnlyAutoProperty);
}

Instead of the diagnostic descriptor, you can also use Diagnostic Id (error code) to identify the issue which should be fixed by tested code fix. This allows testing code fixes which respond to standard C# compiler errors such as CS0736.

Example: Test code refactoring behavior

[Test]
public void SimpleTest()
{
    const string markupCode = @"
class C
{
    void M()
    {
        var s = [|string.Format(""{0}"", 42)|];
    }
}";

    const string expected = @"
class C
{
    void M()
    {
        var s = $""{42}"";
    }
}";

    TestCodeRefactoring(markupCode, expected);
}