there is a way to run tests against only one selected spec file. For doing that, we should configure test.ts file inside src folder. This file contains the below line of code which configures to include test files while running the ng test or ng t command.

const context = require.context('./', true, /\.spec\.ts$/);

The first parameter is the repository path (here, all files of an angular project) the third parameter includes all spec files.

let’s assume now, we have a  “brice.component.spec.ts”  that we want to run a single component test file for debugging and testing it. There are multiple ways we can do it.

configure test.js to execute a single spec file

Replace /\.spec\.ts$/ with the file name you want to test. For example: /brice.component\.spec\.ts$/

then Runs the following command :

ng test [project]
//or 
ng t [project]

This will run test only for app.component.spec.ts.

PS: if we want to run all test spec files inside a folder, we can configure them like this

const context = require.context('./service', true, /\.spec\.ts$/);

this will run all spec files under the service folder.

command line to run single test spec file

use --include

Angular CLI provides the --include option to include a regular expression for including single or multiple files/folders.

ng test --include=**/brice.component.spec.ts // single file
ng test --include'**/service/*.spec.ts // multiple files inside a folder

or

// single file
npm run test -- --include src/app/brice.component.spec.ts

// all files inside the service folder
npm run test -- --include src/app/service

npm script to single test spec file

we can also configure the scripts tag in package.json

{

    "scripts": {
        "singletest": "ng test --include=**/brice.component.spec.ts"
    }
}

then run it with “npm run singletest” command.

jasmine and karma allow executing one component test spec

Jasmine provides fdescribe and fit allowing us to focus specific test cases to run it and skipped non-focused test case execution.

fdescribe('MyComponent', () => {
  fit('should create', () => {
    //test for undefined 
  }
}

• fdescribe -> Allows to run a group of tests
• fit -> Allows running a single test case

PS: Please note that use ddescribe for jasmine version <2.1 version, and use fdescribe for >2.1 version.

mocha and karma allow running a single component spec file

mocha provides describe.only and it.only allowing us to focus specific test cases to run it and skipped non-focused test case execution.

• describe.only– Allows to run a group of tests
• it.only – Allows running a single test case

describe.only('MyComponent', () => {
  it.only('should create', () => {
    //test for undefined 
  }
}