How to test javascript redirection without redirecting?

Question

I'm using Jasmine for some testing, although this can be generally applied to browser-based javascript unit testing.

I have a function that, on certain conditions redirects the user to a different page using window.location.assign. The problem is, if this line is reached, the page is redirected. In this case, since it's redirected to '/', the page reloads, and all the tests run again. What can I do to test that the function reaches the line where it redirects, without redirecting?

Answer 1

I have faced this same problem. My solution was to break out the actual redirect into a single purpose function. That is, don't do any condition checking or other logic, just redirect. Say this is the old code...

function redirect() {
 if(something) {
  window.location = "/";
 else if(somethingElse)
  window.location = "/?a=42";
 else
  window.location = "/derp";
}

I would change that to..

function redirect() {
 if(something) {
  doRedirect("/");
 else if(somethingElse)
  doRedirect("/?a=42");
 else
  doRedirect("/derp");
}

function doRedirect(href) {
 window.location = href;
}

Then you can spyOn the doRedirect function to ensure the redirect function is passing in the correct URI for the conditions.