Moq Skill

Moq is the mocking framework used throughout VanDaemon for unit testing. All services are registered as singletons and depend on interfaces, making them ideal candidates for mocking. Tests use Mock<T> to create test doubles, Setup() to configure behavior, and Verify() to assert interactions.

Quick Start

Basic Service Mock

// Mock a service interface
var mockTankService = new Mock<ITankService>();
mockTankService
    .Setup(x => x.GetAllTanksAsync(It.IsAny<CancellationToken>()))
    .ReturnsAsync(new List<Tank> { new Tank { Id = Guid.NewGuid(), Name = "Fresh Water" } });

var controller = new TanksController(mockTankService.Object);

Mock with Argument Matching

var mockControlService = new Mock<IControlService>();
mockControlService
    .Setup(x => x.SetControlStateAsync(
        It.Is<Guid>(id => id != Guid.Empty),
        It.IsAny<object>(),
        It.IsAny<CancellationToken>()))
    .ReturnsAsync(true);

Key Concepts

Concept	Usage	Example
`Mock<T>`	Create mock instance	`new Mock<ITankService>()`
`.Object`	Get mocked instance	`mock.Object`
`Setup()`	Configure method behavior	`.Setup(x => x.Method())`
`Returns()`	Sync return value	`.Returns(value)`
`ReturnsAsync()`	Async return value	`.ReturnsAsync(value)`
`It.IsAny<T>()`	Match any argument	`It.IsAny<CancellationToken>()`
`It.Is<T>()`	Match with predicate	`It.Is<Guid>(g => g != Guid.Empty)`
`Verify()`	Assert method called	`.Verify(x => x.Method(), Times.Once)`

Common Patterns

Mocking Logger (Serilog via ILogger)

var mockLogger = new Mock<ILogger<TankService>>();
var service = new TankService(mockLogger.Object, mockFileStore.Object);

// Verify logging occurred (Moq can't verify extension methods directly)
// Use LoggerFactory or just trust the implementation

Mocking JsonFileStore

var mockFileStore = new Mock<IJsonFileStore>();
mockFileStore
    .Setup(x => x.LoadAsync<List<Tank>>("tanks.json", It.IsAny<CancellationToken>()))
    .ReturnsAsync(testTanks);

Mocking SignalR Hub Context

var mockHubContext = new Mock<IHubContext<TelemetryHub>>();
var mockClients = new Mock<IHubClients>();
var mockGroup = new Mock<IClientProxy>();

mockHubContext.Setup(x => x.Clients).Returns(mockClients.Object);
mockClients.Setup(x => x.Group("tanks")).Returns(mockGroup.Object);

Related Skills

See the xunit skill for test structure and assertions
See the fluent-assertions skill for readable assertions
See the csharp skill for async/await patterns used with mocks

moq