Running a single test file

Question

Is there a way to run ng test for a single file instead of for the entire test suite? Ideally, I'd like to get the quickest possible feedback loop when I'm editing a file, but karma executes the whole suite on each save, which is a bit slow when you build up a big enough test suite.

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This is different from How to execute only one test spec with angular-cli in that that question is about running an individual spec. This is about running an individual file. The solution involves the same Jasmine spec feature, but the nature of the question is slightly different.

Answer 1

I discovered that Jasmine allows you to prefix describe and it methods with an f (for focus): fdescribe and fit. If you use either of these, Karma will only run the relevant tests. To focus the current file, you can just take the top level describe and change it to fdescribe. If you use Jasmine prior to version 2.1, the focusing keywords are: iit and ddescribe.

This example code runs just the first test:

// Jasmine versions >/=2.1 use 'fdescribe'; versions <2.1 use 'ddescribe'
fdescribe('MySpec1', function () {
    it('should do something', function () {
        // ...
    });
});

describe('MyOtherSpec', function () {
    it('should do something else', function () {
        // ...
    });
});

Here is the Jasmine documentation on Focusing Specs, and here is a related SO article that provides additional thoughtful solutions.