未调用 xUnit 设置函数

Question

I have a very basic unit test. For some reason the test passed only the first time but all subsequent calls have failed. Here is the test code:

private Mock<IMyInterface> _mockObject;
public Test() {
   _mockObject = new Mock<IMyInterface>();
}

[Fact]
public void ItReturnsTheRightThing() {
   _mockObject.SetUp(o => o.FunctionIWantToMock()).Returns(new SpecialObject(true));
   var classIWantToTest = new ClassIWantToTest(_mockObject.Object);
   classIWantToTest.RunCode();
   ...
}

The interface:

internal interface IMyInterface {
    SpecialObject FunctionIWantToMock();
}

The production code:

public class ClassIWantToTest {
    IMyInterface _client;
    internal ClassIWantToTest(IMyInterface client) {
        _client = client;
    }
    public bool RunCode() {
        SpecialObject so = _client.FunctionIWantToMock();
        return so.Value; // This line is the problem
        ...
    }
}

The problem is that when I run my test, my mock function isn't returning what I setup in the SetUp function, it's not returning the SpecialObject(true) but rather null . I then get a null reference exception. When I debug the test, I can't step into the _client.FunctionIWantToMock call, it just immediately steps to the next line and populates so with null.

Answer 1

Since this doesn't make a whole lot of sense, I would try something like this:

[Fact]
public void ItReturnsTheRightThing() {
    _mockObject = new Mock<IMyInterface>();
   _mockObject.SetUp(o => o.FunctionIWantToMock()).Returns(new SpecialObject(true));
   var classIWantToTest = new ClassIWantToTest(_mockObject.Object);
   classIWantToTest.RunCode();
  ...
}

Try this and if it works, something interferes with the mock object in between

Answer 2

A coworker helped me figure out the issue. It is also my fault that I obfuscated too much of the original code when writing up this question.

The problem was that I was passing explicit parameters to the o.FunctionIWantToMock() method during the setup, that did not match the explicit parameters passed to the function in the business logic. So the actual test code was o.FunctionIWantToMock("foo", "bar") . In my business logic, the actual function is called with _client.FunctionIWantToMock("Foo", "Bar") . So because the parameters didn't match ("Foo" vs "foo", "Bar" vs "bar") the SetUp wasnt actually setting up my actual code. I changed the setUp function to

o.FunctionIWantToMock(It.IsAny<string>(), It.IsAny<string>())