PosInfoMoq2010.md

PosInfoMoq2010: Mock.Of<T> method must be used only with types that contains parameterless contructor

Property	Value
Rule ID	PosInfoMoq2010
Title	Mock.Of<T> method must be used only with types that contains parameterless contructor.
Category	Compilation
Default severity	Error

Cause

The Mock.Of<T> method must be used only with types that contains accessible parameterless constructor.

Rule description

The Mock.Of<T> method must be use only for non-sealed classes which contains accessible parameterless constructor.

For example, the following code can not mock the Service class because it does not contain a parameterless constructor.

[Fact]
public void Test()
{
	var service = Mock.Of<Service>(s => s.Property == 1234);		// The Service can not be mocked, because not parameterless constructor exists.
}

public class Service
{
	public Service(int timeout)
	{
	}

	public virtual int Property { get; }
}

In this other example, the Service class cannot be mocked too because it contains a private constructor.

[Fact]
public void Test()
{
	var service = Mock.Of<Service>();		// The Service can not be mocked, because the parameterless constructor is private.
}

public class Service
{
	private Service()
	{
	}

	public virtual int Property { get; }
}

How to fix violations

To fix a violation of this rule, be sure to the mocked type contains an accessible parameterless constructor (public, protected or internal)

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 "Can not instantiate proxy of class: xxx. Could not find a parameterless constructor. (Parameter 'constructorArguments')" message.