Generating Coverage Data

JavaScript / TypeScript with Jest

Jest has built-in coverage reporting capabilities using Istanbul under the hood.

$
# Add to your package.json or run directly
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"scripts": {
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  "test": "jest --coverage"
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}

By default, Jest will output coverage reports to the coverage directory, including an LCOV report at coverage/lcov.info.

React

If you’re using Create React App, Jest is already configured. Simply run:

$
npm test -- --coverage

Node.js with NYC (Istanbul)

$
# Install NYC
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npm install --save-dev nyc
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>
# Add to your package.json
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"scripts": {
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  "test": "nyc mocha"
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}

NYC will generate an LCOV report at coverage/lcov.info.

Python with pytest

$
# Install pytest-cov
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pip install pytest-cov
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>
# Run tests with coverage
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pytest --cov=. --cov-report=xml

This will generate a coverage report in Cobertura XML format at coverage.xml.

Python with coverage.py

$
# Install coverage.py
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pip install coverage
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>
# Run your tests with coverage
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coverage run -m pytest
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>
# Generate an XML report
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coverage xml

This will also generate a coverage report in Cobertura XML format at coverage.xml.

Ruby with SimpleCov

Add SimpleCov to your Gemfile:

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group :test do
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  gem 'simplecov', require: false
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end

Configure SimpleCov at the top of your test helper file (e.g., test/test_helper.rb or spec/spec_helper.rb):

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require 'simplecov'
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SimpleCov.start
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# Rest of your test helper file...

Run your tests normally:

$
bundle exec rspec
>
# or
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bundle exec rails test

SimpleCov will generate a coverage report at coverage/.resultset.json.

Go

Go has built-in coverage capabilities:

$
# Run tests with coverage
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go test -coverprofile=coverage.out ./...
>
>
# Convert to Clover format for Qlty using goclover
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# First install goclover: go install github.com/t-yuki/goclover@latest
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goclover coverage.out > clover.xml

This will generate a Clover XML report which Qlty can understand.

Java / Kotlin with Gradle and JaCoCo

Add JaCoCo to your Gradle build:

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plugins {
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    id 'jacoco'
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}
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jacoco {
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    toolVersion = "0.8.8"
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}
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jacocoTestReport {
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    reports {
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        xml.required = true
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        csv.required = false
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        html.required = true
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    }
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}

Run tests and generate a JaCoCo report:

$
./gradlew test jacocoTestReport

This will generate an XML report at build/reports/jacoco/test/jacocoTestReport.xml.

Java / Kotlin with Maven and JaCoCo

Add JaCoCo to your Maven pom.xml:

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<plugin>
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    <groupId>org.jacoco</groupId>
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    <artifactId>jacoco-maven-plugin</artifactId>
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    <version>0.8.8</version>
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    <executions>
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        <execution>
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            <goals>
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                <goal>prepare-agent</goal>
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            </goals>
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        </execution>
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        <execution>
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            <id>report</id>
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            <phase>test</phase>
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            <goals>
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                <goal>report</goal>
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            </goals>
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        </execution>
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    </executions>
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</plugin>

Run tests and generate a JaCoCo report:

$
mvn clean test

This will generate an XML report at target/site/jacoco/jacoco.xml.

PHP with PHPUnit

Configure PHPUnit in your phpunit.xml:

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<phpunit>
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    <!-- ... other configuration ... -->
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    <coverage>
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        <report>
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            <clover outputFile="coverage.xml"/>
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        </report>
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    </coverage>
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</phpunit>

Run PHPUnit:

$
phpunit --coverage-clover=coverage.xml

This will generate a Clover XML report at coverage.xml.

Swift with Xcode and slather

First, ensure code coverage is enabled in your Xcode scheme.

Then install slather:

$
gem install slather

Create a .slather.yml file:

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coverage_service: cobertura_xml
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xcodeproj: YourProject.xcodeproj
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scheme: YourScheme
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output_directory: coverage

Run your tests and then generate a coverage report:

$
xcodebuild -project YourProject.xcodeproj -scheme YourScheme -derivedDataPath Build/ -enableCodeCoverage YES test
>
slather

This will generate a Cobertura XML report in the coverage directory.