End to End testing for Lightning Components
Salesforce has plans (Safe-Harbour) to release a testing framework for Lightning but you can use this now.
It's basically a Selenium test written in Lightning flavoured javascript. By testing this way, you can use the test during development to decrease your time to feedback.
Testing components using this technique provides two benefits:
- Normal testing, assertions and regression protection
- Faster development feedback by viewing N copies of your component in different states at the same time
- Works with the LockerService enabled
- Can be used End to End testing full apps a la Selenium or at the smallest component level
- Support for testing Apex calls when loading a component and after user interactions, as well as asserting state changes after Apex calls complete
Production
Sandbox
then change your browser uri to:
- /c/greased_LoginFormTests.app : a sample test for a sample login component
- /c/greased_TestStatusTests.app : tests for the components that make up the tool
The best way to learn how to use the tool is to look at the sample app test and the example assertions test The comments there should be clear but please log an issue if something is not clear and I'll fix it.
The first time you click the button, your browser may block the tabs from opening because of the popup-blocker. If you only only one tab open, find the popup-blocker and disable it for this url.
You can click the Run All button at any time, even if all the tests are already open. Doing so will cause them all to run again. This makes it simple to re-run all tests any time you want to check your changes.
Testing always seems to encourage good design and the same happens with Greased. Public attributes are part of a components API and they are primarily how you drive and assert about the state of components.
API methods (aura:method) are another good way to expose behaviours for testing.
Eventually there will be a @TestVisible equivalent for Lightning. For now there are occasions where you need to expose attributes as public when it doesn't really feel like a public API. A possible alternative
When Apex calls are made, you need to invoke using a function which takes a callback. This allows the test (Promise) to wait for your Apex to return before proceeding. There is an example of this in the sample app/test.
- Jan 11, 2017
- added test.setAttribute
- test.setAttributes to reduce boilerplate in tests
- Jan 20, 2017
- added test.sleep
- Jan 21, 2017
- added javascript assertions
- run all tests at once
- fireApplicationEvent and fireComponentEvent helper fns
- Mar 4th, 2017
- cleaned up performance warnings
- added helper.componentValue to reduce need for focus changes in tests
Since most actions in Lightning are asynchronous, the test scripts are built using chains of Promises. The documentation states that promises are available in all supported browsers.
If you are building components for Communities or Sites then you can't control if your users are using "supported" browsers or not. In that case, you can still use promises in your tests but do not use them in your components. If you do this it also means that you cannot run these tests in the unsupported browsers and that means you lose some valuable automatic testing. For that reason, there is an outstanding issue to provide just enough "then" support as part of Greased so that tests can run in any browser. I'm hoping someone with more javascript skills than me can complete this one because Communities/Sites really need test coverage to be reliable.
The idea of running assertions as an application came from watching https://www.youtube.com/watch?v=Hxmbl2Oj_cM but it didn't work with the LockerService. However only Assertions and Diff are required from QUnit so https://github.com/flitbit/diff works under LockerService. Building assertions on top of this was an easy leap.
The idea of testing N instances of the same component came from https://github.com/bhauman/devcards In Clojurescript development this provides a delightful experience so Greased has it as well.
Kudos to Phillip Clark, Keir Bowden and Bruce Hauman for sharing. This kind of cross-pollination is what OSS is all about.
Finally Inventing on principle is an inspiration to any kind of software development. If you haven't seen it, it's worth the time.
Check the FEATURE issues for new features that would really help everyone who uses this tool. I will sing the praises of anyone who contributes.