PosInformatique.Moq.Analyzers

PosInfoMoq1001: The mocked instances behavior should be defined to Strict mode

Property	Value
Rule ID	PosInfoMoq1001
Title	The mocked instances behavior should be defined to Strict mode
Category	Design
Default severity	Warning

Cause

A mocked instance has been created with the Loose or Default behavior instead of Strict.

Rule description

When instantiating a Mock<T> instance (or using the Mock.Of<T>() alternative), 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 !
}

The same behavior should be defined if the Mock.Of<T>() alternative is used:

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

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

	// 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 or as the last argument of Mock.Of<T>() method.

Visual Studio fixer

A Visual Studio fixer exists to set explicitely the MockBehavior to Strict in the current document, project or solution.

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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