mouseover element not working using protractor

I have a directive that produces the following html structure:

<div class="popover ng-isolate-scope" ng-mouseover="toggle(true)" ng-mouseleave="toggle(false)" popover="" label="hover time!" trigger-class="button" content-class="specialContentClass">  
  <span id="thing" class="popover-trigger button">hover time!</span>
  <div ng-transclude="" ng-show="show" class="popover-content ng-hide">
    <div class="ng-scope">Popover content </div>
  </div>
</div>

The code works fine and the popover content is correctly shown when you mouseover manually using a browser.

I'm trying to test the mouseover functionality with the following protractor test:

 it('should display the popover-content on mouseover', function() {
     browser.get('http://localhost:9000/');
     browser.actions()
     .mouseMove(element(by.css('.popover')).find()).perform();
     expect(element(by.css('.popover-content'))
     .isDisplayed().toBeTruthy());
 });

The test seems to run, the browser opens but I don't see the popup-content displaying before the browser then closes so I'm fairly sure the mousemove bit isn't working for some reason. The following is then output in the terminal:

launcher] 0 instance(s) of WebDriver still running
[launcher] chrome #1 failed 1 test(s)
[launcher] overall: 1 failed spec(s)
[launcher] Process exited with error code 1
ycompu:angular ycompu$  

I've read the documentation and using browser is definitely the right way to approach this test. I'm at a loss as the syntax looks correct to me.