Wait for JavaScript condition in Nightwatch.js

Question

I am new to Nightwatch.js and am moving some tests over from the WD.js library. One nifty feature of WD.js is .waitForConditionInBrowser(), which waits for an arbitrary JavaScript snippet to be truthy. I am however unable to figure out how to interact with the JavaScript this way in Nightwatch.js, or if it's even possible (after perusing the docs). Here is an example of what I want to do:

Let's say I am loading a page where after about 3 seconds my_js_var becomes 5. In WD.js, it would look like this (wait max. 5 seconds):

.get(my_page_url)
.waitForConditionInBrowser('my_js_var === 5', 5000)
// continue if my_js_var === 5 within 5 s

I even tried doing something more dirty in Nightwatch, but I am probably misunderstanding how interaction with page JS works at all:

.url(my_page_url)
.pause(5000)
.execute(function() {
    return (my_js_var === 5);
})
// continue if my_js_var === 5 within 5 s

But it just continues no matter what is returned, and it's unclear where the result goes to.

Is there a proper waitFor function in Nightwatch, and if not, how do I run basic assertions on evaluated JavaScript code?

QualiT · Accepted Answer · 2020-04-06 09:20:39Z

2

It's been a while, but I used to do something like this:

exports.command = function(callback) {
  var self = this;
  this.timeoutsAsyncScript(5000, function() {
    this.executeAsync(function(done) {
        if(my_js_var === 5) {
          return my_js_var === 5
        }
        else {
          done();
        }
      },
      [], 
      function(result) {
        if(typeof(callback) === "function") {
          callback.call(self, result);
        }
      });
  });
  return this;
};

The timeout in timeoutsAsyncScript lets you assure a reasonable wait time so that the test can fail accordingly when it should fail.

answered Apr 6, 2020 at 9:20

QualiT

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