使用 Moq 模拟惰性接口

我想要模拟惰性接口，但我得到了object reference not set to an instance of an object例外。

‌这是正在测试的类：

public class ProductServiceService : IProductServiceService
{
    private readonly Lazy<IProductServiceRepository> _productServiceRepository;
    private readonly Lazy<IProductPackageRepository> _productPackageRepository;

    public ProductServiceService(
        Lazy<IProductServiceRepository> productServiceRepository,
        Lazy<IProductPackageRepository> productPackageRepository)
    {
        _productServiceRepository = productServiceRepository;
        _productPackageRepository = productPackageRepository;
    }

    public async Task<OperationResult> ValidateServiceAsync(ProductServiceEntity service)
    {
        var errors = new List<ValidationResult>();

        if (!await _productPackageRepository.Value.AnyAsync(p => p.Id == service.PackageId))
            errors.Add(new ValidationResult(string.Format(NameMessageResource.NotFoundError, NameMessageResource.ProductPackage)));
       .
       .
       .
        return errors.Any()
            ? OperationResult.Failed(errors.ToArray())
            : OperationResult.Success();
    }
}

这是测试课

[Fact, Trait("Category", "Product")]
public async Task Create_Service_With_Null_Financial_ContactPerson_Should_Fail()
{
    // Arrange
    var entity = ObjectFactory.Service.CreateService(packageId: 1);

    var mockProductServiceRepository = new Mock<Lazy<IProductServiceRepository>>();

    var repo = new Mock<IProductPackageRepository>();
    repo.Setup(r => r.AnyAsync(It.IsAny<Expression<Func<ProductPackageEntity, bool>>>()));
    var mockProductPackageRepository = new Lazy<IProductPackageRepository>(() => repo.Object);

    var sut = new ProductServiceService(mockProductServiceRepository.Object, mockProductPackageRepository);

    // Act
    var result = await sut.AddServiceAsync(service);

    // Assert
    Assert.False(result.Succeeded);
    Assert.Contains(result.ErrorMessages, error => error.Contains(string.Format(NameMessageResource.NotFoundError, NameMessageResource.ProductPackage)));
}

mockProductPackageRepository始终为空。我关注了这篇博文，但仍然遇到空引用异常。

如何使用 Moq 在 C# 单元测试中模拟对象的延迟初始化

Update: here is a screen that indicates fakeProductPackageRepository is null.

这是您的示例的重构版本：

[Fact, Trait("Category", "Product")]
public async Task Create_Service_With_Null_Financial_ContactPerson_Should_Fail() {
    // Arrange
    var entity = ObjectFactory.Service.CreateService(packageId = 1);

    var productServiceRepositoryMock = new Mock<IProductServiceRepository>();

    var productPackageRepositoryMock = new Mock<IProductPackageRepository>();
    productPackageRepositoryMock
        .Setup(repository => repository.AnyAsync(It.IsAny<Expression<Func<ProductPackageEntity, bool>>>()))
        .ReturnsAsync(false);

    //Make use of the Lazy<T>(Func<T>()) constructor to return the mock instances
    var lazyProductPackageRepository = new Lazy<IProductPackageRepository>(() => productPackageRepositoryMock.Object);
    var lazyProductServiceRepository = new Lazy<IProductServiceRepository>(() => productServiceRepositoryMock.Object);

    var sut = new ProductServiceService(lazyProductServiceRepository, lazyProductPackageRepository);

    // Act
    var result = await sut.AddServiceAsync(service);

    // Assert
    Assert.False(result.Succeeded);
    Assert.Contains(result.ErrorMessages, error => error.Contains(string.Format(NameMessageResource.NotFoundError, NameMessageResource.ProductPackage)));
}

UPDATE

下列最小、完整且可验证的示例您所陈述的问题经测试后通过。

[TestClass]
public class MockLazyOfTWithMoqTest {
    [TestMethod]
    public async Task Method_Under_Test_Should_Return_True() {
        // Arrange
        var productServiceRepositoryMock = new Mock<IProductServiceRepository>();

        var productPackageRepositoryMock = new Mock<IProductPackageRepository>();
        productPackageRepositoryMock
            .Setup(repository => repository.AnyAsync())
            .ReturnsAsync(false);

        //Make use of the Lazy<T>(Func<T>()) constructor to return the mock instances
        var lazyProductPackageRepository = new Lazy<IProductPackageRepository>(() => productPackageRepositoryMock.Object);
        var lazyProductServiceRepository = new Lazy<IProductServiceRepository>(() => productServiceRepositoryMock.Object);

        var sut = new ProductServiceService(lazyProductServiceRepository, lazyProductPackageRepository);

        // Act
        var result = await sut.MethodUnderTest();

        // Assert
        Assert.IsTrue(result);
    }

    public interface IProductServiceService { }
    public interface IProductServiceRepository { }
    public interface IProductPackageRepository { Task<bool> AnyAsync();}

    public class ProductServiceService : IProductServiceService {
        private readonly Lazy<IProductServiceRepository> _repository;
        private readonly Lazy<IProductPackageRepository> _productPackageRepository;

        public ProductServiceService(
            Lazy<IProductServiceRepository> repository,
            Lazy<IProductPackageRepository> productPackageRepository) {
            _repository = repository;
            _productPackageRepository = productPackageRepository;
        }

        public async Task<bool> MethodUnderTest() {
            var errors = new List<ValidationResult>();

            if (!await _productPackageRepository.Value.AnyAsync())
                errors.Add(new ValidationResult("error"));

            return errors.Any();
        }
    }
}