public void TestSetsDisplayTestBackToInitialMessageIfCoinPurseIsZero()
        {
            TextBox displayTextBox = new TextBox();
            MockCoinPurse mockCoinPurse = new MockCoinPurse {AmountAvailableToReturn = 0.99m};

            VendingDisplayController displayController = new VendingDisplayController(displayTextBox, mockCoinPurse);

            displayController.CoinPurseUpdated();

            Assert.AreNotEqual("INSERT COINS", displayTextBox.Text);

            mockCoinPurse.AmountAvailableToReturn = 0;
            displayController.CoinPurseUpdated();

            Assert.AreEqual("INSERT COINS", displayTextBox.Text);
        }
        public void TestSetsCurrentPurseValueFormatedLikeMoneyWhenCoinPurseNotifiesAmountHasChanged(decimal purseValue,
            string expectedDisplayText)
        {
            TextBox displayTextBox = new TextBox();
            MockCoinPurse mockCoinPurse = new MockCoinPurse {AmountAvailableToReturn = purseValue};

            VendingDisplayController displayController = new VendingDisplayController(displayTextBox, mockCoinPurse);

            displayController.CoinPurseUpdated();

            Assert.AreEqual(expectedDisplayText, displayTextBox.Text);
        }