Jasmine: How to test a user input?

I wrote the following html file:

<!DOCTYPE html> <html lang="en"> <head>
    <meta charset="UTF-8">
    <title></title> </head> <body>
    <h1> HELLO WORLD </h1>
    <button type="button"> CLICK HERE</button>
    <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.1.1/jquery.min.js"></script>
    <script>
        $('button').click(function() {
            $('h1').text("Thank you");
            var ans = prompt("Please type your age");
            if (ans > 80) {
                $('h1').text("You're old");
            }
        })
    </script> </body> </html>

I want to test that once the user clicks on the button and gives an age older than 80, the page behaves as expected and the h1-tag text changes to "You're old".

My question is how to write a Jasmine spec to test this feature?

Solution

You need to use "Spy" object to intercept "prompt" function and return your own value. After check the caption text. The code may look like ...

deascribe("test inline function:", function() {
  it("caption should be 'too old' for age of more than 80", function () {
    spyOn(window, 'prompt').and.returnValue(81);
    $('button').click();
    expect($('h1').text()).toBe("You're old");
  });
});