PosInformatique.Moq.Analyzers

PosInfoMoq2013: The delegate in the argument of the Returns()/ReturnsAsync() method must have the same parameter types of the mocked method/property.

Property	Value
Rule ID	PosInfoMoq2013
Title	The delegate in the argument of the Returns()/ReturnsAsync() method must have the same parameter types of the mocked method/property.
Category	Compilation
Default severity	Error

Cause

The delegate in the argument of the Returns()/ReturnsAsync() method must have the same parameter types of the mocked method/property.

Rule description

The lambda expression, anonymous method or method in the argument of the Returns() must have the same parameter types of the mocked method/property.

NB: Moq allows to pass a delegate with no argument in the Returns()/ReturnsAsync() method even the setup method contains arguments.

[Fact]
public void Test()
{
    var validMock = new Mock<IService>();
    validMock.Setup(s => s.GetData(1234))
    .Returns((int a) =>                     // OK, the mocked GetData() take a int value as argument.
        {
            return 1234;
        });
    validMock.Setup(s => s.GetData(1234))
        .Returns(() =>                      // OK, Moq allows no arguments.
        {
            return 1234;
        });
    validMock.Setup(s => s.IsAvailable)     // OK, property don't have arguments.
        .Returns(() =>
        {
            return true;
        });

    var invalidMock = new Mock<IService>();
    invalidMock.Setup(s => s.GetData(1234))
        .Returns((string s) =>              // Error, the mocked GetData() take a int value as argument.
        {
            return "Foobar";
        });
    invalidMock.Setup(s => s.IsAvailable)
        .Returns((string s) =>              // Error, mocked property have no arguments.
        {
            return "Foobar";
        });
}

public interface IService
{
    int GetData(int id);

    bool IsAvailable { get; }
}

How to fix violations

To fix a violation of this rule, be sure the lambda expression, anonymous method or method as parameter of the Returns()/ReturnsAsync() method must have the same arguments type of the setup property/method.

When to suppress warnings

Do not suppress an error from this rule. If bypassed, the execution of the unit test will be failed with a ArgumentException thrown with the “Object of type ‘xxx’ cannot be converted to type ‘yyy’.” message.

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