public void TestA()
        {
            Mock <IServiceA> serviceA = new Mock <IServiceA>();

            var value = "ABC";

            serviceA.Setup(s => s.ReturnValue(It.IsAny <string>())).Returns(value);

            var serviceB = new ServiceB(serviceA.Object);

            serviceB.returnValue(true, value);

            serviceA.Verify(mock => mock.ReturnValue(It.IsAny <string>()), Times.Once());
        }
        public void TestB()
        {
            Mock <IServiceA> serviceA = new Mock <IServiceA>();

            var value = "ABC";

            serviceA.Setup(s => s.ReturnValue(It.IsAny <string>())).Returns("ABCDEF");

            var serviceB = new ServiceB(serviceA.Object);

            serviceB.returnValue(false, value);

            serviceA.Verify(mock => mock.ReturnValue(It.IsAny <string>()), Times.Never());
        }