public void AddBalls_MachineWithoutBalls_MachineWithAddedBalls() { //Arrange _gumballMachineWithStateMock.SetupProperty(c => c.BallsCount, 0u); _gumballMachineWithStateMock.Setup(c => c.SetNoQuarterState()).Verifiable(); //Act _soldOutState.AddBalls(3); //Assert Assert.Equal(3u, _gumballMachineWithStateMock.Object.BallsCount); _gumballMachineWithStateMock.Verify(c => c.SetNoQuarterState()); }