mock javascript alert, confirm, prompt

mock_dialogs.js

var MockPrompt = {
  install: function() {
    MockPrompt.message = undefined;
    MockPrompt.value = undefined;
    MockPrompt.returnValue = undefined;
    MockPrompt.originalPrompt = window.prompt;

    window.prompt = function(message, value) {
      MockPrompt.message = message;
      MockPrompt.value = value;
      return MockPrompt.returnValue;
    };
  },

  uninstall: function() {
    window.prompt = MockPrompt.originalPrompt;
  },

  willReturn: function(returnValue) {
    MockPrompt.returnValue = returnValue;
  }
};

var MockConfirm = {
  install: function() {
    MockConfirm.message = undefined;
    MockConfirm.returnValue = true;
    MockConfirm.originalConfirm = window.confirm;

    window.confirm = function(message) {
      MockConfirm.message = message;
      return MockConfirm.returnValue;
    };
  },

  uninstall: function() {
    window.confirm = MockConfirm.originalConfirm;
  },

  willReturn: function(returnValue) {
    MockConfirm.returnValue = returnValue;
  }
};

var MockAlert = {
  install: function() {
    MockAlert.message = undefined;
    MockAlert.originalAlert = window.alert;

    window.alert = function(message) {
      MockAlert.message = message;
    };
  },

  uninstall: function() {
    MockAlert.originalAlert = window.alert;
  }
};

var MockDialogs = {
  install: function() {
    MockAlert.install();
    MockPrompt.install();
    MockConfirm.install();
  },

  uninstall: function() {
    MockAlert.uninstall();
    MockPrompt.uninstall();
    MockConfirm.uninstall();
  }
};

mock_dialogs_test.js

function setUp() {
  MockDialogs.install();
}

function tearDown() {
  MockDialogs.uninstall();
}
  
function testMockPrompt() {
  MockPrompt.willReturn("goodbye");
  assertEquals("goodbye", prompt("hello", "default"));
  assertEquals("hello", MockPrompt.message);
  assertEquals("default", MockPrompt.value);
}

function testMockConfirm() {
  assertTrue(confirm("are you sure"));
  assertEquals("are you sure", MockConfirm.message);
}

function testMockConfirmReturnsFalse() {
  MockConfirm.willReturn(false);
  assertFalse(confirm("are you sure"));
}

function testMockAlert() {
  alert("ouch!");
  assertEquals("ouch!", MockAlert.message);
}