Which is better Jest or Mocha?
There are many tools available to the JavaScript programmer, but two of the most popular are Jest and Mocha. These frameworks function in very similar ways, but there are several reasons to choose one over the other.
The first is popularity: Jest has almost twice as many stars on GitHub as Mocha does. This popularity is due in part to how easy it is to wrap a test file with a describe block, each describe block being able to contain any number of it blocks. The describe blocks are used to organize tests into different groups, and each of the it blocks contains an individual unit test or set of tests.
Jest also supports mocking out dependencies that should be excluded from tests, whereas Mocha forces you to use stubs instead. However, Mocha’s mocking library provides several methods that Jest’s doesn’t allow for mocking out behavior that isn’t directly exposed by the dependency (such as mockedXhr in AngularJS).
Jest also lets you specify a timeout for how long a test should be allowed to run before being interrupted and categorized as a failure, whereas Mocha doesn’t have this feature available at all.
With these points considered, it can be argued that Jest has more flexibility than Mocha.