Troubleshooting.md

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Uh oh, something went wrong? Use this guide to resolve issues with Jest.

Tests are Failing and You Don't Know Why

Try using the debugger built into >= Node 6.3.

Place a debugger; statement in any of your tests, and then, in your project's directory, run:

node --debug-brk --inspect ./node_modules/.bin/jest -i [any other arguments here]

This will output a link that you can open in Chrome. After opening that link, the Chrome Developer Tools will be displayed, and a breakpoint will be set at the first line of the Jest CLI script (this is done simply to give you time to open the developer tools and to prevent Jest from executing before you have time to do so). Click the button that looks like a "play" button in the upper right hand side of the screen to continue execution. When Jest executes the test that contains the debugger statement, execution will pause and you can examine the current scope and call stack.

Note: the -i cli option makes sure Jest runs test in the same process rather than spawning processes for individual tests. Normally Jest parallelizes test runs across processes but it is hard to debug many processes at the same time.

More information on the V8 inspector can be found here: https://nodejs.org/api/debugger.html#debugger_v8_inspector_integration_for_node_js

Caching Issues

The preprocessor script was changed or babel was updated and the changes aren't being recognized by Jest?

Retry with --no-cache.

Explanation: Jest caches transformed module files to speed up test execution. If you are using your own custom preprocessor, consider adding a getCacheKey function to it: getCacheKey in Relay.

Unresolved Promises

If a promise doesn't resolve at all, this error might be thrown:

- Error: Timeout - Async callback was not invoked within timeout specified by jasmine.DEFAULT_TIMEOUT_INTERVAL.`

Most commonly this is being caused by conflicting Promise implementations. Consider replacing the global promise implementation with your own, for example global.Promise = require.requireActual('promise'); and/or consolidate the used Promise libraries to a single one.

If your test is long running, you may want to consider to increase the timeout specified in jasmine.DEFAULT_TIMEOUT_INTERVAL.

jasmine.DEFAULT_TIMEOUT_INTERVAL = 10000; // 10 second timeout

Watchman Issues

Try running Jest with --no-watchman or set the watchman configuration option to false.

Also see watchman troubleshooting.

I'm using npm3 and my node_modules aren't properly loading.

Upgrade jest-cli to 0.9.0 or above.

I'm using babel and my unmocked imports aren't working?

Upgrade jest-cli to 0.9.0 or above.

Explanation:

jest.dontMock('foo');

import foo from './foo';

In ES2015, import statements get hoisted before all other

var foo = require('foo');
jest.dontMock('foo'); // Oops!

In Jest 0.9.0, a new API jest.unmock was introduced. Together with a plugin for babel, this will now work properly when using babel-jest:

jest.unmock('foo'); // Use unmock!

import foo from './foo';

// foo is not mocked!

See the Getting Started guide on how to enable babel support.

I upgraded to Jest 0.9.0 and my tests are now failing?

Jest is now using Jasmine 2 by default. It should be easy to upgrade using the Jasmine upgrade guide.

If you would like to continue using Jasmine 1, set the testRunner config option to jasmine1 or pass --testRunner=jasmine1 as a command line option.

Compatibility issues

Jest takes advantage of new features added to Node 4. We recommend that you upgrade to the latest stable release of Node. The minimum supported version is v4.0.0. Versions 0.x.x are not supported.

Still unresolved?

See Support.