PosInformatique.Moq.Analyzers

PosInfoMoq1001: The Mock<T> instance behavior should be defined to Strict mode

Property	Value
Rule ID	PosInfoMoq1001
Title	The Mock<T> instance behavior should be defined to Strict mode
Category	Design
Default severity	Warning

Cause

A Mock instance has been created with the `Loose` behavior instead of `Strict`.

Rule description

When instantiating a Mock<T> instance, the MockBehavior of the Mock instance should be defined to Strict.

By default, Moq build instances of mocked instance which have a Loose behavior for non-setup methods.

For example with the following code:

public interface IRepository
{
    int GetData();
}

public class CustomerService
{
	private readonly IRepository repository;

    public CustomerService(IRepository repository)
	{
		this.repository = repository;
	}

	public int GetDataFromRepository()
	{
		return this.repository.GetData();
	}
}

If a Mock<T> instance of IRepository is created with the Loose behavior (default behavior of Moq) and the GetData() method has not been setup, the default int value (0) will be returned.

[Fact]
public void GetDataFromRepository()
{
	// Arrange
	var repository = new Mock<IRepository>();		// Default behavior (Loose)

	//  /!\ No methods on the IRepository has been setup !
	
	var service = new CustomerService(repository.Object);

	// Act
	var result = service.GetDataFromRepository();	// "result" will be defined to 0.
}

To fix the violation of this rule for the previous example, set the MockBehavior to Strict in the constructor of the Mock<T> class.

[Fact]
public void GetDataFromRepository()
{
	// Arrange
	var repository = new Mock<IRepository>(MockBehavior.Strict);		// Strict behavior (Loose)

	//  /!\ No methods on the IRepository has been setup !
	
	var service = new CustomerService(repository.Object);

	// Act
	var result = service.GetDataFromRepository();	// A "MoqException" will be raised to indicate that the GetData() method has not been setup !
}

How to fix violations

To fix a violation of this rule, set the MockBehavior to Strict in the constructor of the Mock<T> class.

When to suppress warnings

Do not suppress a warning from this rule. Normally all methods called on a mocked instance must be setup.

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