Simulating a Sequenced Behavior

A sequenced behavior occurs when the same method has a different behavior each time the method is called.

When to Use

When you want to simulate a sequenced behavior.

After using a sequence and calling the method with the expected behavior, you can use WhenCalled on the method again. In this case, the old behavior sequence is reset, and a new one starts from the next WhenCalled.

Syntax

C#

Isolate.WhenCalled(() => fakeDependency.GetID()).<behavior>;
Isolate.WhenCalled(() => fakeDependency.GetID()).<behavior>;
...


VB

Isolate.WhenCalled(Function() fakeDependency.GetID()).<behavior>
Isolate.WhenCalled(Function() fakeDependency.GetID()).<behavior>
...

The last call to Isolate.WhenCalled() defines the default behavior for the method from that moment onwards.

Samples

C#

// Note: Use Isolated to clean up after the test
[TestMethod, Isolated] 
public void SequencedWillReturn_Example()
{
  var fakeDependency = Isolate.Fake.Instance<Dependency>();
  // Sequenced calls will return values in sequence, last value will stay the default
  Isolate.WhenCalled(() => fakeDependency.GetID()).WillReturn(2);
  Isolate.WhenCalled(() => fakeDependency.GetID()).WillReturn(9);

  var result = new ClassUnderTest().AddToDependency3Times(1, fakeDependency);
  Assert.AreEqual(21, result);
}

public int AddToDependency3Times(int a, Dependency dependency)
{
  return a + dependency.GetID() + dependency.GetID() + dependency.GetID();
}


VB

' Note: Use Isolated to clean up after the test
<TestMethod(), Isolated()> _
Public Sub SequencedWillReturn_Example()
    Dim fakeDependency = Isolate.Fake.Instance(Of Dependency)()
    ' Sequenced calls will return values in sequence, last value will stay the default
    Isolate.WhenCalled(Function() fakeDependency.GetID()).WillReturn(2)
    Isolate.WhenCalled(Function() fakeDependency.GetID()).WillReturn(9)

    Dim result = New ClassUnderTest().AddToDependency3Times(1, fakeDependency)
    Assert.AreEqual(21, result)
End Sub
	
Public Function AddToDependency3Times(a As Integer, dependency As Dependency) As Integer
  Return a + dependency.GetID() + dependency.GetID() + dependency.GetID()
End Function

The WillReturnCollectionValuesOf() method is not sequential.
Meaning that if you set two diffrent behaviors that returns two diffrent collections to the same method it will only use the first one.