copilot-agentic-workshop: Instructions file for GitHub Copilot

Test Conventions

Stack

• Framework: xUnit
• Assertions: FluentAssertions (result.Should().Be(...))
• Mocking: NSubstitute (Substitute.For<T>())

Never use Moq, MSTest, or manual fake classes unless explicitly requested.

Test Class Structure

public sealed class ClassNameTests
{
    // Dependencies substituted via NSubstitute
    private readonly IDependency _dep = Substitute.For<IDependency>();

    // System under test
    private readonly ClassName _sut;

    public ClassNameTests() => _sut = new ClassName(_dep);

    [Fact]
    public async Task MethodName_Scenario_ExpectedResult()
    {
        // Arrange
        _dep.SomeMethod(Arg.Any<string>()).Returns("value");

        // Act
        var result = await _sut.MethodName("input");

        // Assert
        result.Should().NotBeNull();
        result.Value.Should().Be("expected");
    }
}

Naming Convention

MethodName_Scenario_ExpectedResult

Examples:

• CreateAsync_WithValidRequest_ReturnsCreatedTask
• GetByIdAsync_WhenTaskDoesNotExist_ReturnsNull
• Complete_WhenAlreadyDone_ThrowsInvalidOperationException

FluentAssertions Patterns

// Equality
result.Should().Be(expected);
result.Should().NotBe(unexpected);

// Nullability
result.Should().NotBeNull();
result.Should().BeNull();

// Collections
list.Should().HaveCount(3);
list.Should().ContainSingle(x => x.Id == id);
list.Should().BeEmpty();

// Exceptions
var act = async () => await _sut.Method();
await act.Should().ThrowAsync<InvalidOperationException>()
         .WithMessage("*partial match*");

// Strings
str.Should().StartWith("prefix");
str.Should().NotBeNullOrWhiteSpace();

// Dates
dt.Should().BeCloseTo(DateTimeOffset.UtcNow, TimeSpan.FromSeconds(1));

NSubstitute Patterns

// Return value
_repo.GetByIdAsync(id, Arg.Any<CancellationToken>()).Returns(task);

// Return argument
_repo.AddAsync(Arg.Any<TaskItem>(), Arg.Any<CancellationToken>())
     .Returns(x => x.Arg<TaskItem>());

// Verify call
await _repo.Received(1).DeleteAsync(id, Arg.Any<CancellationToken>());