Useful design patterns for unit testing/TDD?

Question

Reading this question has helped me solidify some of the problems I\'ve always had with unit-testing, TDD, et al.

Since coming across the TDD approach to development I k

Answer 1

Arrange, Act, Assert is a good example of a pattern that helps you structure your testing code around particular use cases.

Here's some hypothetical C# code that demonstrates the pattern.

[TestFixture]
public class TestSomeUseCases() {

    // Service we want to test
    private TestableServiceImplementation service;

    // IoC-injected mock of service that's needed for TestableServiceImplementation
    private Mock dependencyMock;

    public void Arrange() {
        // Create a mock of auxiliary service
        dependencyMock = new Mock();
        dependencyMock.Setup(s => s.GetFirstNumber(It.IsAny)).Return(1);

        // Create a tested service and inject the mock instance
        service = new TestableServiceImplementation(dependencyMock.Object);
    }

    public void Act() {
        service.ProcessFirstNumber();
    }

    [SetUp]
    public void Setup() {
        Arrange();
        Act();
    }

    [Test]
    public void Assert_That_First_Number_Was_Processed() {
        dependencyMock.Verify(d => d.GetFirstNumber(It.IsAny()), Times.Exactly(1));
    }
}

If you have a lot of scenarios to test, you can extract a common abstract class with concrete Arrange & Act bits (or just Arrange) and implement the remaining abstract bits & test functions in the inherited classes that group test functions.