BehaviorCoupledVsNot.cs

public class NotBehaviorCoupledTests
{
  // GOOD
  Fake<IMyDependency> _myDependency;
  IMyService _myService;
  
  [TestInitialize]
  public void Initialize()
  {
    _myDependency = A.Fake<IMyDependency>();
    _myService = new MyService(_myDependency.FakeObject);
  }
  
  [TestMethod]
  public void A_call_to_thing_should_return_child_object()
  {
    // Arrange behavior
    var childObject = new object();
    A.CallTo(() => _myDependency.GetChildObject()).Returns(childObject);
    
    // Act
    var result = _myService.GetThing();
    
    // Assert
    Assert.AreEqual(childObject, result);
  }
}

public class BehaviorCoupledTests
{
  // BAD
  Fake<IMyDependency> _myDependency;
  IMyService _myService;
  
  [TestInitialize]
  public void Initialize()
  {
    _myDependency = A.Fake<IMyDependency>();
    _myService = new MyService(_myDependency.FakeObject);
    
    // Arrange behavior
    var childObject = new object();
    A.CallTo(() => _myDependency.GetChildObject()).Returns(childObject);
  }
  
  [TestMethod]
  public void A_call_to_thing_should_return_child_object()
  {
    // Act
    var result = _myService.GetThing();
    
    // Assert
    Assert.AreEqual(childObject, result);
  }
}