How to write a Jest configuration file

Question

I am trying to pass along a configuration file to Jest in order to run tests only from a given directory.

According to documentation, you can use config.testPathDirs: https://facebook.github.io/jest/docs/api.html#config-testpathdirs-array-string and you can call jest --config=<config-file>.

Unfortunately the documentation doesn't include any description of how the configuration file should look like.

I tried both these options in a jest-config.js file:

testPathDirs = ['coredata/src']; 

and

config.testPathDirs(['coredata/src']); 

and ran:

$ jest --config=jest-config.js 

...but I get this type of error:

$ jest --config=jest-config.js Using Jest CLI v0.4.0 Failed with unexpected error.  /Users/carles/dev/azazo/coredata/node_modules/jest-cli/src/jest.js:179       throw error;             ^ SyntaxError: Unexpected token c     at Object.parse (native)     at /Users/carles/dev/azazo/coredata/node_modules/jest-cli/src/lib/utils.js:291:23     at _fulfilled (/Users/carles/dev/azazo/coredata/node_modules/jest-cli/node_modules/q/q.js:798:54)     at self.promiseDispatch.done (/Users/carles/dev/azazo/coredata/node_modules/jest-cli/node_modules/q/q.js:827:30)     at Promise.promise.promiseDispatch (/Users/carles/dev/azazo/coredata/node_modules/jest-cli/node_modules/q/q.js:760:13)     at /Users/carles/dev/azazo/coredata/node_modules/jest-cli/node_modules/q/q.js:574:44     at flush (/Users/carles/dev/azazo/coredata/node_modules/jest-cli/node_modules/q/q.js:108:17)     at process._tickCallback (node.js:419:13) 

Answer 1

I figured out that the config file is JSON.

{   "testPathDirs": ["coredata/src"] } 

Unfortunately I found nowhere in the documentation a hint about this.