Asserting an element is focused

问题

According to the How do I assert an element is focused? thread, you can check if an element is focused by switching to an activeElement() and assert this is the same element you've expected to have the focus:

expect(page.element.getAttribute('id')).toEqual(browser.driver.switchTo().activeElement().getAttribute('id'));

In my case, the currently focused element does not have an id attribute.

What should I do instead of checking an id?

Bonus question: Also, as you can see from my tries to solve it, it looks like I cannot expect/assert an element (or web element) as a complete object. Why?

---

I've tried:

expect(page.element).toEqual(browser.driver.switchTo().activeElement());

But is is failing with an error I cannot even understand - there is a huge traceback (it is about 10 minutes to scroll in the console), but no user-friendly error inside.

I've also tried to use getWebElement():

expect(page.element.getWebElement()).toEqual(browser.driver.switchTo().activeElement());

But this resulted into the following error:

Error: expect called with WebElement argument, expected a Promise. Did you mean to use .getText()?

Using the latest protractor development version.

回答1:

In my answer I'm going to assume activeElem and pageElem are both protractor element finders, and are pointing to the same web element.

First to answer your question about why

expect(activeElem).toEqual(pageElem);

Gets into an infinite loop, it's because protractor patched jasmine's expect to resolve the promise before asserting, so that things like expect(activeElem.getText()).toEqual('text'); works without having to do

activeElem.getText().then(function(text) {
  expect(text).toEqual('text');
})

You could say, why not just resolve the promise once? But then there are nested promises.

So now you might be thinking this is an issue, but it really isn't because you would never compare two elementFinders in a real use case. Jasmine's toEqual does a reference check, and not a deep compare, so expect(activeElem).toEqual(pageElem), is just the same as a simple reference comparison: (activeElem === pageElem).toToTruthy(), and there's really no point doing that. (Note element(by.css('html')) === element(by.css('html')) is false because it's not the same reference.)

So, to answer the real question for this thread: how to see if two elementFinders have the same underlying webelements:

expect(activeElem.getId()).toEqual(pageElem.getId());

回答2:

It's weird that it's expecting a promise only and could not handle a webdriver element... I had the same HUGE stacktrace as you.

Anyway, would you accept this kind of solution: send a "dumb" promise with a nice comment to justify why you had to do that. It's more a workaround than a semantic solution I admit.

expect(page.element.getInnerHtml())
  .toEqual(browser.driver.switchTo().activeElement().getInnerHtml());

It's working for me ;)

EDIT: Bonus answer

The reason you can't call expect with a WebElement comes from the Webdriver Control Flow Principle (I'm sure you already know about) and this line in jasminewd, the adapter for jasmine to Webdriver developped and used by Protractor ;)

回答3:

For the future readers, I've created a custom matcher to assert if an element is active/focused:

beforeEach(function() {
    jasmine.addMatchers({
        toBeActive: function() {
            return {
                compare: function(elm) {
                    return {
                        pass: elm.getId().then(function (activeElementID) {
                            return browser.driver.switchTo().activeElement().getId().then(function (currentElementID) {
                                return jasmine.matchersUtil.equals(currentElementID, activeElementID);
                            });
                        })
                    };
                }
            };
        }
    });
});

Usage:

expect(element(by.css("#myid")).toBeActive();

回答4:

What about using CSS selectors and :focus

expect(element.all(by.css('#myid:focus')).count()).toBe(1);

回答5:

I solved it by using protractor's: ElementFinder.prototype.equals

const activeElement = await browser.driver.switchTo().activeElement();
const potentialyFocusedElement = await component.$('your-locator');
const isFocused = await potentialyFocusedElement.equals(activeElement);

I am not sure how exactly equals work, if it does a deep compare, or it somehow compares instances. But it works.

Note that you can not call activeElement.equals(...) since it is not an ElementFinder, it is a WebElement.

回答6:

You need to come up with a way to tell Protractor/webdriver how to find your element on the page. Protractor uses JavaScript to find elements, so any of the tools available for inspecting the DOM are available. Protractor and webdriver wrap these APIs in the various by flavors:

http://angular.github.io/protractor/#/api?view=ProtractorBy

In addition to the basic flavors, Protractor adds Angular-aware flavors (so you can search by Angular binding, etc).

If your element does not have any distinguishing characteristics, then it might be worth adding something to make it easier to test. Or, (though this is often frowned upon because its so fragile), you can use an xpath. See https://github.com/angular/protractor/blob/master/docs/locators.md

回答7:

You can simply check the text (or anything else) of the element:

var currentElement = browser.switchTo().activeElement();
expect(currentElement.getText()).toEqual(page.element.getText());

来源：https://stackoverflow.com/questions/28679364/asserting-an-element-is-focused