write-tests

Instructions

Read the target file(s), understand all its public methods and behaviors, then generate a comprehensive test class following the conventions below.

Test Conventions

Project and Namespace

• One test class per production class.
• Test class goes in the project with the same name and a .UTest suffix
• Test namespace mirrors the production namespace with .UTest inserted after the project name.
• There should be a static TestHelpers class in the root of the .UTest project for helper methods and test data generation.
• The TestHelpers class should always have a Gen<T>() method for generating random values of any type of the form public static T Gen<T>() => Fixture.Create<T>();.
• There should be a GlobalUsings.cs file in the root of the .UTest project with using statements for all the testing specific namespaces. It should have a global using static TestHelpers.
• Test class name: <ClassName>Tests.

Test Method Naming

• Format: <MethodName>_Should<ExpectedBehavior>_When<Conditions>.
• Drop _When<Conditions> if there are no unique conditions.

Test Paths

• Tests should cover all code but it is not necessary to cover every unique path.
• Tests should assert every output or state change that results from the method under test.

Test Structure

• Divide each test into three sections separated by comments: // given, // when, // then.
• Creating the system under test must be the last statement in the // given section.
• Use Assert.That syntax for all assertions.
• Do NOT use Assert.Multiple.
• Use [TestCase] attribute when testing multiple scenarios for the same method.

Variables and Readability

• No test instance variables — all state is local to each test method.
• Use Gen<T>() for values unless the value has an important meaning.
• Use descriptive variable names for values that do matter, including the system under test.
• Add comments to indicate the purpose of important values.

IMPORTANT: Mocking

• Always use Create<ClassName>() methods to create and setup these mock objects at the bottom of the test class.
• Create methods that are or likely to be used by multiple tests should be moved to the TestHelpers class at the root of the UTest project.
• The Create methods should NEVER return mocks.
• Use Mock.Get to get the underlying mock when Verify is needed.
• Create methods can call other create methods only with parameterless calls
• Create calls should always use named parameters.
• Helper methods should have optional parameters with sensible defaults so tests only specify what they care about.

Formatting

• No regions
• Use file-scoped namespaces
• Don't use sut as a variable name use a meaningful name

Workflow

1. Read the target file and identify all public methods/properties to test
2. Read existing tests in the .UTest project for patterns and available test helpers
3. Use TestHelpers for Gen() and Create methods common to multiple tests.
4. Write the test file in the correct location
5. Build with dotnet build <TestProject>.csproj
6. Run tests with dotnet test <TestProject>.csproj --filter "FullyQualifiedName~<TestClassName>"
7. Fix any failures and re-run until all tests pass