Mock Virtual and Abstract Methods and Properties

Like interfaces, virtual and abstract methods are fundamental pillars of software design. Virtual methods typically have an implementation that can be overridden in a derived class. In comparison, an abstract method (or property) is simply a declaration of a method without an implementation, which must be provided in a derived class.

With JustMock, you can arrange the behavior of a virtual or abstract method or property in the same way you would arrange any other method.

Here is an example of how to mock an abstract method with JustMock:

public abstract class Shape
{
    public double X { get; set; }
    public double Y { get; set; }
 
    public abstract double CalculateArea();
}
 
...
 
[TestMethod]
public void MockAbstractMethod()
{
    // Arrange
    Shape shapeMock = Mock.Create<Shape>();
    Mock.Arrange(() => shapeMock.CalculateArea()).Returns(42);
 
    // Act
    double actualResult = shapeMock.CalculateArea();
 
    // Assert
    Assert.AreEqual(42, actualResult);
}

Here is how to mock a virtual method with JustMock, using the same approach:

public abstract class Shape
{
    public double X { get; set; }
    public double Y { get; set; }
 
    public virtual double CalculateArea()
    {
        return X * Y;
    }
}
 
...
 
[TestMethod]
public void MockAbstractMethod()
{
    // Arrange
    Shape shapeMock = Mock.Create<Shape>();
    Mock.Arrange(() => shapeMock.CalculateArea()).Returns(42);
 
    // Act
    double actualResult = shapeMock.CalculateArea();
 
    // Assert
    Assert.AreEqual(42, actualResult);
}

Mocking properties is similar to mocking methods. Here’s how to mock a property getter with JustMock:

public interface IFoo 
{ 
    int Value{get; set;} 
} 
 
...
 
[TestMethod] 
public void ShouldFakePropertyGet() 
{ 
    // Arrange 
    var foo = Mock.Create<IFoo>(); 
  
    Mock.Arrange(() => foo.Value).Returns(25); 
  
    // Act 
    var actual = foo.Value; 
  
    // Assert 
    Assert.AreEqual(25, actual); 
}

Mock a property getter documentation

Mocking a property setter differs from mocking a property getter as it requires you to use another method due to a limitation in LAMBDA expressions to process the assignment operator:

[TestMethod] 
public void ShouldAssertPropertySet() 
{ 
    // Arrange 
    var foo = Mock.Create<IFoo>(); 
  
    Mock.ArrangeSet(() => foo.Value = 1); 
  
    // Act 
    foo.Value = 1; 
  
    // Assert 
    Mock.AssertSet(() => foo.Value = 1); 
}

Mock a property setter documentation