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| author | Winnie Hellmann <winnie@gitlab.com> | 2019-06-25 10:48:02 +0000 |
|---|---|---|
| committer | Winnie Hellmann <winnie@gitlab.com> | 2019-06-26 10:36:00 +0200 |
| commit | 00c94bad51ae0cda8b3fd416ee064b4af81935c2 (patch) | |
| tree | 1d4aac03c306cdf52bade0d0380adbed39f4f579 | |
| parent | 235d87777e611c57a6d7e44b32f863672d3d5bc6 (diff) | |
| download | gitlab-ce-winh-jsdom-limitations-docs.tar.gz | |
Document limitations of jsdomwinh-jsdom-limitations-docs
| -rw-r--r-- | doc/development/testing_guide/frontend_testing.md | 13 |
1 files changed, 12 insertions, 1 deletions
diff --git a/doc/development/testing_guide/frontend_testing.md b/doc/development/testing_guide/frontend_testing.md index fc9b175bc8a..f3b661b9d30 100644 --- a/doc/development/testing_guide/frontend_testing.md +++ b/doc/development/testing_guide/frontend_testing.md @@ -27,7 +27,7 @@ we need to solve before being able to use Jest for all our needs. ### Differences to Karma - Jest runs in a Node.js environment, not in a browser. Support for running Jest tests in a browser [is planned](https://gitlab.com/gitlab-org/gitlab-ce/issues/58205). -- Because Jest runs in a Node.js environment, it uses [jsdom](https://github.com/jsdom/jsdom) by default. +- Because Jest runs in a Node.js environment, it uses [jsdom](https://github.com/jsdom/jsdom) by default. (see also [limitations](#limitations-of-jsdom) below) - Jest does not have access to Webpack loaders or aliases. The aliases used by Jest are defined in its [own config](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/jest.config.js). - All calls to `setTimeout` and `setInterval` are mocked away. See also [Jest Timer Mocks](https://jestjs.io/docs/en/timer-mocks). @@ -40,6 +40,17 @@ we need to solve before being able to use Jest for all our needs. - Unhandled Promise rejections. - Calls to `console.warn`, including warnings from libraries like Vue. +### Limitations of jsdom + +As mentioned [above](#differences-to-karma), Jest uses jsdom instead of running in a browser. +This comes with a number of limitations, namely: + +- [no scrolling support](https://github.com/jsdom/jsdom/blob/15.1.1/lib/jsdom/browser/Window.js#L623-L625) +- [no element sizes or positions](https://github.com/jsdom/jsdom/blob/15.1.1/lib/jsdom/living/nodes/Element-impl.js#L334-L371) +- [no layout engine](https://github.com/jsdom/jsdom/issues/1322) in general + +We have [#58205](https://gitlab.com/gitlab-org/gitlab-ce/issues/58205) to add support for running Jest in a browser. + ### Debugging Jest tests Running `yarn jest-debug` will run Jest in debug mode, allowing you to debug/inspect as described in the [Jest docs](https://jestjs.io/docs/en/troubleshooting#tests-are-failing-and-you-don-t-know-why). |