jacoco

Original：🇺🇸 English

Translated

JaCoCo Java code coverage tool USE WHEN: user mentions "JaCoCo", "Java coverage", "code coverage", asks about "coverage threshold", "jacoco-maven-plugin", "coverage report", "LINE coverage", "BRANCH coverage" DO NOT USE FOR: JavaScript/TypeScript coverage - use Vitest skill, SonarQube analysis - use `sonarqube` skill, test execution - use testing skills

2installs

Sourceclaude-dev-suite/claude-dev-suite

Added on2026-03-12

NPX Install

npx skill4agent add claude-dev-suite/claude-dev-suite jacoco

SKILL.md Content

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JaCoCo - Quick Reference

When to Use This Skill

Configure code coverage in Java/Maven projects
Set coverage thresholds
Integrate coverage in CI/CD

When NOT to Use This Skill

JavaScript/TypeScript coverage - Use Vitest skill for frontend coverage
SonarQube configuration - Use
```
sonarqube
```
skill for quality gates
Test writing - Use Spring Boot Test or JUnit skills
Gradle projects - JaCoCo works but syntax differs from Maven

Deep Knowledge: Use
mcp__documentation__fetch_docs
with technology:
jacoco
for comprehensive documentation.

Essential Patterns

Maven Configuration

xml

<plugin>
    <groupId>org.jacoco</groupId>
    <artifactId>jacoco-maven-plugin</artifactId>
    <version>0.8.12</version>
    <executions>
        <execution>
            <id>prepare-agent</id>
            <goals><goal>prepare-agent</goal></goals>
        </execution>
        <execution>
            <id>report</id>
            <phase>test</phase>
            <goals><goal>report</goal></goals>
        </execution>
        <execution>
            <id>check</id>
            <goals><goal>check</goal></goals>
            <configuration>
                <rules>
                    <rule>
                        <element>BUNDLE</element>
                        <limits>
                            <limit>
                                <counter>LINE</counter>
                                <value>COVEREDRATIO</value>
                                <minimum>0.80</minimum>
                            </limit>
                        </limits>
                    </rule>
                </rules>
            </configuration>
        </execution>
    </executions>
</plugin>

Exclusions

xml

<excludes>
    <exclude>com.company.config.*</exclude>
    <exclude>com.company.dto.*</exclude>
    <exclude>com.company.entity.*</exclude>
    <exclude>com.company.mapper.*Impl</exclude>
</excludes>

Commands

bash

mvn clean verify           # Test + coverage check
mvn jacoco:report          # Generate report
open target/site/jacoco/index.html  # View report

Counter Types

Counter	Description
`LINE`	Lines of code
`BRANCH`	Branch if/switch
`METHOD`	Methods

Anti-Patterns

Anti-Pattern	Why It's Bad	Correct Approach
Aiming for 100% coverage	Diminishing returns, test bloat	Target 80% LINE, 70% BRANCH
Including DTOs/entities in coverage	Inflates numbers, no logic to test	Exclude with `<excludes>`
Only checking LINE coverage	Misses untested branches	Check both LINE and BRANCH
No coverage threshold in CI	Can't enforce quality	Add `<check>` goal with minimums
Excluding too much code	False sense of security	Only exclude generated/config code
Not versioning jacoco.exec	Can't track coverage trends	Archive reports in CI

Quick Troubleshooting

Issue	Likely Cause	Solution
Coverage report shows 0%	Tests not running with agent	Ensure `prepare-agent` goal runs before tests
Build fails on coverage check	Coverage below threshold	Add tests or adjust minimum in `<limit>`
Report excludes nothing	Wrong exclude pattern	Use fully qualified names (com.company.dto.*)
Report missing classes	Classes not loaded during tests	Add integration tests to cover them
Coverage lower in CI than local	Different test execution	Ensure CI runs all test phases
SonarQube shows no coverage	Wrong report path	Check `sonar.coverage.jacoco.xmlReportPaths`