ImplementorTests.cs

[Test]
public void DoWork_VerifyParentWorkAndChildWorkCalls_Test () {
    // Arrange
    _parentMock.Setup (m => m.ParentWork ()).Verifiable ();
    _parentMock.As<IChildInterface> ().Setup (m => m.ChildWork ()).Verifiable ();
    var implementor = new Implementor (_parentMock.Object);

    // Act
    implementor.DoWork ();

    // Assert
    _parentMock.Verify (m => m.ParentWork (), Times.Once ());
    _parentMock.As<IChildInterface> ().Verify (m => m.ChildWork (), Times.Once ());
}