Mocking 一个惰性接口导致运行时异常

Question

I'm having difficulties while trying to properly mock an arbitrary interface wrapped inside Lazy class.

I've tried:

[TestClass]
public class MyFooTests
{
    private Mock<Lazy<IFoo>> _lazyFooMock = new Mock<Lazy<IFoo>>();
    private Mock<IFoo> _fooMock = new Mock<IFoo>();
    private MyFoo _service;

    [TestMethod]
    public void FooMethod_HappyPath_ShouldReturn()
    {
        //Arrange
        _fooMock
            .Setup(x => x.DoSomething())
            .Returns(1);

        _lazyFooMock
            .SetupGet(x => x.Value)
            .Returns(_fooMock.Object); // --------> Throws Exception.

        _service = new MyService(_lazyFooMock.Object);
    }
}

public interface IFoo
{
    int DoSomething();
}

public class MyFoo
{
    public MyFoo(IFoo foo) { ... }
}

Exception Message:

Unsupported expression: x => x.Value Non-overridable members (here: Lazy.get_Value) may not be used in setup / verification expressions.

Stack Trace:

at Moq.Guard.IsOverridable(MethodInfo method, Expression expression) in C:\projects\moq4\src\Moq\Guard.cs:line 99 at Moq.InvocationShape..ctor(LambdaExpression expression, MethodInfo method, IReadOnlyList 1 arguments, Boolean exactGenericTypeArguments, Boolean skipMatcherInitialization, Boolean allowNonOverridable) in C:\projects\moq4\src\Moq\InvocationShape.cs:line 84 at Moq.ExpressionExtensions.<Split>g__Split|5_0(Expression e, Expression& r, InvocationShape& p, Boolean assignment, Boolean allowNonOverridableLastProperty) in C:\projects\moq4\src\Moq\ExpressionExtensions.cs:line 324 at Moq.ExpressionExtensions.Split(LambdaExpression expression, Boolean allowNonOverridableLastProperty) in C:\projects\moq4\src\Moq\ExpressionExtensions.cs:line 149 at Moq.Mock.Setup(Mock mock, LambdaExpression expression, Condition condition) in C:\projects\moq4\src\Moq\Mock.cs:line 505 at Moq.Mock.SetupGet(Mock mock, LambdaExpression expression, Condition condition) in C:\projects\moq4\src\Moq\Mock.cs:line 520 at Moq.Mock 1 arguments, Boolean exactGenericTypeArguments, Boolean skipMatcherInitialization, Boolean allowNonOverridable) in C:\projects\moq4\src\Moq\InvocationShape.cs:line 84 at Moq.ExpressionExtensions.<Split>g__Split|5_0(Expression e, Expression& r, InvocationShape& p, Boolean assignment, Boolean allowNonOverridableLastProperty) in C:\projects\moq4\src\Moq\ExpressionExtensions.cs:line 324 at Moq.ExpressionExtensions.Split(LambdaExpression expression, Boolean allowNonOverridableLastProperty) in C:\projects\moq4\src\Moq\ExpressionExtensions.cs:line 149 at Moq.Mock.Setup(Mock mock, LambdaExpression expression, Condition condition) in C:\projects\moq4\src\Moq\Mock.cs:line 505 at Moq.Mock.SetupGet(Mock mock, LambdaExpression expression, Condition condition) in C:\projects\moq4\src\Moq\Mock.cs:line 520 at Moq.Mock 1.SetupGet[TProperty](Expression 1 expression) in C:\projects\moq4\src\Moq\Mock 1.cs:line 476 at ** .MyFooTests.FooMethod_HappyPath_ShouldReturn() in C:* **.cs:line 109

Moq: 4.16.1

Answer 1

Solved by help of others, I've dumped the _lazyFooMock and replaced it with actual Lazy: _lazyFoo , and initiated it by the help of the overload: public Lazy(Func<T> valueFactory) .

private Mock<IFoo> _fooMock = new Mock<IFoo>();
private Lazy<IFoo> _lazyFoo;

private MyService _service;

[TestMethod]
public void FooMethod_HappyPath_ShouldReturn()
{
    //Arrange
    _fooMock
        .Setup(x => x.DoSomething())
        .Returns(1);

    _lazyFoo = new Lazy<IFoo>(() => _fooMock.Object);

    _service = new MyService(_lazyFoo);
}