Jest coverage diff

Use the action to get jest coverage diff for pull requests as a comment on the pull request Helps the code reviewer to get the high level view of code coverage changes without leaving the pull request window

example: Code coverage comparison master vs testBranch:

File	% Stmts	% Branch	% Funcs	% Lines
total	99.55 97.73	100 96.97	97.96 95.92	99.54 97.7
src/Error/TestError.ts	100 77.78	100 100	100 66.67	100 77.78
src/Utility/Utility.ts	96.67 90	100 75	88.89 88.89	96.67 90

How It Works

uses the following jest command to get code coverage summary as json for the pull request.

npx jest --coverage --coverageReporters="json-summary"

Then switches branch to the base branch on which the pull request has been raised and runs the same command again. Calculates the diff between the two reports to figure out additions, removals, increase or decrease in code coverage. And then posts that diff as a comment on the PR

NOTE : The action will work perfectly only for pull requests. Have not been tested with other events or on schedule workflows

Configuration

The action assumes jest configuration and jest module already present in the workflow and uses the installed module and the already present config to run the tests.

Sample workflow for running this action

name: Node.js CI

on: pull_request

jobs:
  build:
    strategy:
      matrix:
        node-version: [14.x]
        platform: [ubuntu-latest]
    runs-on: ${{ matrix.platform }}
    steps:
    - uses: actions/checkout@v2
    - name: Use Node.js ${{ matrix.node-version }}
      uses: actions/setup-node@v1
      with:
        node-version: ${{ matrix.node-version }}
    - run: npm ci
    - name: TestCoverage
      id: testCovergae
      uses: anuraag016/Jest-Coverage-Diff@master
      with:
        fullCoverageDiff: false // defaults to false, if made true whole coverage report is commented with the diff