Unit Test Standards

Purpose

Unit tests verify small pieces of behaviour quickly and deterministically.

AIC Standard

• xUnit is the default test framework for new AIC .NET projects.

• Tests must be deterministic and isolated.

• Tests should run from the command line using dotnet test.

• Tests should not depend on external services.

• Unit tests must not use production databases, real message brokers or real customer services.

Naming

Use behaviour-based names:

public sealed class AccessDecisionServiceTests
{
    [Fact]
    public void CanReadCase_WhenUserHasMatchingClearance_ReturnsTrue()
    {
    }
}

Structure

Use Arrange, Act, Assert:

[Fact]
public void CalculatePriority_WhenCaseIsUrgent_ReturnsHigh()
{
    var caseRecord = CaseRecordBuilder.New().WithUrgency(Urgency.Urgent).Build();
    var calculator = new CasePriorityCalculator();

    var priority = calculator.Calculate(caseRecord);

    priority.ShouldBe(Priority.High);
}

Test Data Builders

Use builders to make intent clear:

var caseRecord = CaseRecordBuilder.New()
    .WithStatus(CaseStatus.Open)
    .WithOwner("user-123")
    .Build();

Mocking Rules

• Mock external dependencies, not value objects.

• Prefer real domain objects.

• Do not over-mock internal implementation.

• Avoid verifying every method call unless behaviour requires it.

• Mock time through IClock or TimeProvider.

Unit Test Gate

Unit tests must:

• run quickly

• be included in PR pipeline

• be named clearly

• fail for one understandable reason

• use stable data

• avoid sleeps and timing assumptions