Testing Domain Services Code

Domain Services components are plain .NET classes — services take repository interfaces, repositories return Maybe<T>. There's no framework magic to work around in tests.

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Testing a service with JsonRepository (no mocks)

JsonRepository<TEntity, TId> writes to a real file. In tests, point it at a temp path so each test gets a clean slate and nothing leaks to disk permanently.

using DHI.Services;
using DHI.Services.Jobs;
using Xunit;

public class JobServiceTests : IDisposable
{
    private readonly string _tempFile;
    private readonly JobService<object, string> _svc;

    public JobServiceTests()
    {
        _tempFile = Path.GetTempFileName();
        var repo = new JobRepository(_tempFile);
        _svc = new JobService<object, string>(repo, null, null);
    }

    [Fact]
    public void Add_ThenGet_ReturnsJob()
    {
        var job = new Job<Guid, string>(Guid.NewGuid(), "RunReport", "admin");
        _svc.Add(job);

        var found = _svc.TryGet(job.Id, out var result);

        Assert.True(found);
        Assert.Equal("RunReport", result.TaskId);
    }

    public void Dispose() => File.Delete(_tempFile);
}

Key points: - Path.GetTempFileName() creates a unique file each test run. - IDisposable.Dispose cleans up — xUnit calls it after each test class instance. - No async, no mocking library, no in-memory database setup needed.

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Testing a service with a mock repository

When you want to test service logic in isolation (e.g., lifecycle events, guards), mock the repository interface instead. Any mocking library works; example uses NSubstitute:

using NSubstitute;
using DHI.Services;

public class SensorServiceTests
{
    [Fact]
    public void Add_RaisesAddedEvent()
    {
        var repo = Substitute.For<ISensorRepository>();
        var svc = new SensorService(repo);

        bool eventRaised = false;
        svc.Added += (_, _) => eventRaised = true;

        svc.Add(new Sensor(Guid.NewGuid(), "CTD #1", "mS/cm"));

        Assert.True(eventRaised);
    }
}

Mock the interface (ISensorRepository), not the concrete class. The service only depends on the interface.

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Testing with multiple providers in the same test suite

If you have integration tests that run against different providers (JSON for CI, PostgreSQL for local), use a factory method or fixture that picks the repository based on an environment variable:

static ISensorRepository CreateRepo()
{
    var conn = Environment.GetEnvironmentVariable("TEST_SENSOR_CONN");
    if (string.IsNullOrEmpty(conn))
        return new SensorRepository(Path.GetTempFileName());

    // PostgreSQL or other provider
    return new PgSensorRepository(conn);
}

This keeps tests runnable in CI without a database while still supporting full integration runs locally.

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What not to test

• Don't test JsonRepository serialization — that's the framework's job.
• Don't test Maybe<T> operators — they're tested in the core package.
• Test your business logic — the guards you add, the lifecycle event handlers, the derived queries.