Code Coverage and Reporting - CircleCI Tutorial

Introduction

Code coverage is a metric that measures the degree to which your source code is tested by your test suite. CircleCI allows you to measure code coverage and generate reports, providing insights into the effectiveness of your tests and helping you identify areas that require more attention. This tutorial will guide you through the process of implementing code coverage and generating reports in CircleCI.

Example

Let's consider an example where we measure code coverage using Istanbul for a Node.js application:


    version: 2.1

    jobs:

      test:

        docker:

          - image: circleci/node:12

        steps:

          - checkout

          - restore_cache:

            keys:

              - v1-dependencies-{{ checksum "package-lock.json" }}

          - run: npm install

          - save_cache:

            paths:

              - ./node_modules

            key: v1-dependencies-{{ checksum "package-lock.json" }}

          - run:

            name: Run Tests with Coverage

            command: npm run test -- --coverage

Code Coverage and Reporting in CircleCI

To implement code coverage and generate reports in CircleCI, follow these steps:

1. Choose a code coverage tool

Select a code coverage tool that is compatible with your programming language and test framework. Popular code coverage tools include Istanbul, JaCoCo, and coverage.py.

2. Configure your test environment

Ensure that your test environment is set up to collect code coverage information. This typically involves instrumenting your code during the testing process to track which parts of the code are executed.

3. Generate code coverage reports

Configure your CI/CD pipeline to generate code coverage reports after running the tests. This may involve specifying additional commands or options to your test command, instructing the code coverage tool to collect coverage data and generate reports.

For example, if you are using Istanbul as your code coverage tool for a Node.js application, you can modify your CircleCI configuration file to run tests with coverage using the following command:


    steps:

        - run:

          name: Run Tests with Coverage

          command: npm run test -- --coverage

Common Mistakes

Not configuring the test environment to collect code coverage data
Forgetting to generate code coverage reports after running the tests
Not considering code coverage as part of the testing strategy

Frequently Asked Questions (FAQs)

What is a good code coverage percentage?

There is no universally defined threshold for a good code coverage percentage. The appropriate coverage percentage depends on various factors such as the project's complexity, the criticality of the code, and industry best practices. It is recommended to aim for as high a coverage percentage as possible while considering practical constraints.
How can I view code coverage reports in CircleCI?

Code coverage reports can be generated in various formats such as HTML, XML, or JSON. You can configure your CI/CD pipeline to store the generated reports as artifacts, allowing you to view and analyze them within the CircleCI interface or download them for further examination.
Can I enforce a minimum code coverage requirement in CircleCI?

Yes, you can configure CircleCI to fail the build or trigger a notification if the code coverage falls below a certain threshold. This helps ensure that code changes maintain or improve code coverage levels.

Summary

In this tutorial, you learned how to measure code coverage and generate reports in CircleCI to assess the effectiveness of your tests. By choosing a code coverage tool, configuring the test environment, and generating reports, you can gain insights into the quality and coverage of your code. Use code coverage reports to identify areas that require additional testing and improve the overall reliability of your software. Regularly monitor code coverage metrics and adjust your testing strategy accordingly. Refer to the CircleCI documentation and the documentation of your chosen code coverage tool for further details and advanced configuration options.