Publishing Merged Code Coverage Report of Nx Workspace in Azure CI Pipeline

6 minute read

If you are working on Nx Monorepo workspace and have many angular projects. And if you are using Azure CI/CD Pipeline then you might aware that there is no inbuilt azure task which will combine all of your code coverage xml. Therefore, the only workaround is you must consolidated all code coverage reports in one and publish that merged one only.

What is Code Coverage Report in Azure CI Pipeline

Code coverage helps you determine the proportion of your project’s code that is actually being tested by tests such as unit tests. To increase your confidence of the code changes, and guard effectively against bugs Learn More…

Reviewing the code coverage result helps to identify code path(s) that are not covered by the tests. This information is important to improve the test collateral over time by reducing the test debt.

You can see at file level in azure pipeline

Azure devops does not merge multiple code coverage reports

At present, the code coverage reporting functionality provided by this task is limited and it does not merge coverage data. If you provide multiple files as input to the task, only the first match is considered. If you use multiple publish code coverage tasks in the pipeline, the summary and report is shown for the last task. Any previously uploaded data is ignored. Learn more…

However, Azure Devops supports merging multiple test results and display out of the box. Check Publish Test Results Nx Monorepo Angular Azure Pipelines article to learn more.

Installing Cobertura-merge npm package

At this time Azure Pipeline only support showing code coverage using Cobertura or JaCoCo coverage formats only. I am using Cobertura in order to publish code coverage.

cobertura-merge is the npm package is a Utility to merge multiple cobertura xml files into one. I will use this npm package to merge my all code-coverage files.

In case cobertura-merge is failing to install or failing to run and you are in windows machine then run below script:

npm --add-python-to-path='true' --debug install --global windows-build-tools

Installing Glob npm package

We have nested code-coverage files so, I want to search all of the file path. Therefore, I am installing glob npm package to do that for me. Glob npm package: Matches files using the patterns the shell uses, like stars and stuff.

Folder structure of multiple code coverage files

Since I have a Nrwl.Nx monorepo which has angular apps and libs. And when I run the test using --codeCoverage=true then it creates the cobertura-coverage.xml files. Read [Publish Code Coverage Nx Monorepo Angular in Azure Pipelines] to learn how to publish code coverage to azure pipeline.

Notice, I have coverage files from applications (apps) and libraries (libs)

Finding all Coverage File paths

We need to get the path of each cobertura-coverage.xml file.

Lets create a merge-codecoverage.js JavaScript file to search all xml files we will use glob npm package.

const glob = require('glob');
const path = require('path');

const targetDir = path.resolve(__dirname, '../../coverage');

glob(targetDir + '/**/*.xml', {}, (err, files) => {
  console.log(files);
});

[
  "c:/Full Stack Master/Fullstackmaster COURSES/Mono Repo Course/temp/nx-monorepo-angular/coverage/apps/cutepuppies-admin/cobertura-coverage.xml",
  "c:/Full Stack Master/Fullstackmaster COURSES/Mono Repo Course/temp/nx-monorepo-angular/coverage/apps/cutepuppies-client/cobertura-coverage.xml",
  "c:/Full Stack Master/Fullstackmaster COURSES/Mono Repo Course/temp/nx-monorepo-angular/coverage/libs/branding/logger/cobertura-coverage.xml",
]

Debugging JavaScript in VS Code

Read this article to learn How to debug Node.JS Code in VsCode

Move All Cobertura Coverage Xml to Merge Folder

Install fs-extra which will help us to copy all of the coverage file in merge folder and then we will user cobertura-merge npm package to crate single merged-cobertura-coverage.xml file.

function copyCodeCoverageToMergedFolder() {
  const coverageDir = path.resolve(__dirname, '../../coverage');
  const mergedDir = path.join(coverageDir, '/merged');
  const files = glob(coverageDir + '/**/*.xml', { sync: true });

  files.forEach((f, i) => {
    const x = `${path.basename(f)}-${i}.xml`; // creating unique file name
    fs.copySync(f, `${mergedDir}/${x}`);
  });
}

Merging All Cobertura Coverage Xml to Single Report

We will create merged-cobertura-coverage.xml which is combined of all of the report files.

In order to merge all of them we need below script.

npx cobertura-merge -o merged-cobertura-coverage.xml package1=cobertura-coverage.xml-0.xml package2=cobertura-coverage.xml-1.xml package3=cobertura-coverage.xml-2.xml

Running the cobertura-merge script

Merged file created inside the merged folder

Merged cobertura-coverage.xml file

Here is the JavaScript for merging code coverage files.

function mergeCodeCoverage() {
  const files = glob(mergedDir + '/**/*.xml', { sync: true });

  const packages = files
    .map((f, i) => `package${i + 1}=${path.basename(f)}`)
    .join(' ');
  const script = `cobertura-merge -o merged-cobertura-coverage.xml ${packages}`;

  execSync(script, {
    stdio: [0, 1, 2],
    cwd: mergedDir,
  });
}

Updating Azure Pipeline to publish code coverage

Use below task to publish merged code coverage report in azure pipeline.

# Publish Code Coverage Results
- task: PublishCodeCoverageResults@1
  enabled: false
  displayName: Code Coverage
  inputs:
    codeCoverageTool: 'Cobertura'
    summaryFileLocation: '$(Build.SourcesDirectory)/coverage/merged/merged-cobertura-coverage.xml'
  condition: |
    and(
      succeeded(),
      not(contains(
          variables['COMMANDS'],
          '"test":[]'
      ))
    )

Identify How many projects are affected

I changed the logging.service.ts in branding service. Which is used by both apps.

Run nx affected:dep-graph --base=main

Running azure pipeline for nx monorepo

Now lets run the azure pipeline and see if we can see the 3 projects code coverage is shown in merged fashion.

See 3 tests are running in azure pipeline

publishing code coverage in azure pipeline

Notice it published the code coverage report for all 3 projects.

Excluding files from code coverage

I want to exclude the src folder root files from code coverage. We dont want to show test.ts or polyfills.ts coverage report.

Go to workspace.json file and identify your project names and in the test configuration insert code coverage exclude file list like below screenshot.

"codeCoverageExclude": [
          "apps/cutepuppies-client/src/test.ts",
          "apps/cutepuppies-client/src/polyfills.ts"
        ],

Now run nx run cutepuppies-client:test --codeCoverage=true

Now notice we do not have src folder files code coverage.

Lets do this exclude for all of our project’s test configuration.

Showing Project Names in Merged Code Coverage Report

Notice, I have code coverage from below projects.

I want to show the project names in the Code Coverage Report of Azure pipeline. Therefore, we will update the JavaScript code to put correct project name per code coverage file in our merged code coverage xml file. Like Below:

I need to generate & run below cobertura merge script to create correct merged code coverage file with project names.

npx cobertura-merge -o merged-cobertura-coverage.xml cutepuppies-admin=apps-cutepuppies-admin-cobertura-coverage.xml cutepuppies-client=apps-cutepuppies-client-cobertura-coverage.xml branding-logger=libs-branding-logger-cobertura-coverage.xml branding-ngmaterial=libs-branding-ngmaterial-cobertura-coverage.xml customers-users=libs-customers-users-cobertura-coverage.xml sales-puppies=libs-sales-puppies-cobertura-coverage.xml sales-puppy-editor=libs-sales-puppy-editor-cobertura-coverage.xml

Change the merge code coverage in JavaScript

function mergeCodeCoverage() {
  copyCodeCoverageToMergedFolder();

  const files = glob(mergedDir + '/**/*.xml', { sync: true });

  const packages = files
    .map((f, i) => {
      const fileName = path.basename(f);
      const projectName = projects.filter((p) => fileName.search(p) > -1).pop();

      return `${projectName}=${fileName}`;
    })
    .join(' ');

  const script = `npx cobertura-merge -o merged-cobertura-coverage.xml ${packages}`;

  execSync(script, {
    stdio: [0, 1, 2],
    cwd: mergedDir,
  });
}

function copyCodeCoverageToMergedFolder() {
  fs.emptyDirSync(mergedDir);
  const files = glob(coverageDir + '/**/*.xml', { sync: true });

  files.forEach((f, i) => {
    const x = f.split('/coverage/')[1].replace(/\//g, '-').split('/').pop();
    fs.copySync(f, `${mergedDir}/${x}`);
  });
}

Running Azure pipeline & Showing Nx Monorepo All Projects Code Coverage

Now you must call the above JavaScript from azure-pipelines.yml file.

🏃 Run your pipeline

💯 Showing Code Coverage percentages

:hugging_face: Notice now we see our code coverage per application and the correct file names.

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