Java — Failing Unit Test Example¶

What do you want?¶

Goal	Command
Fix a broken Maven/Gradle build	`code-agent experts run bug-fix --log /tmp/mvn.log --verify-cmd "mvn test -q" -w .`
Increase coverage	`code-agent run "add unit tests to raise coverage" --verify-cmd "mvn test -q" -w .`
PR line review	`code-agent experts run code-review --pr N -w .`

Java uses JUnit + Maven or Gradle. Set --verify-cmd to match your build tool.

Home quick start (binary first): Get started · Use cases

Parser note

Dedicated Java/JUnit log parser is limited — bug-fix uses generic error parsing plus the agent reading test output. --verify-cmd is critical so the agent proves mvn test or ./gradlew test passes.

Option A — Maven project¶

1. Create a failing test¶

mkdir -p /tmp/java-demo && cd /tmp/java-demo
git init

mvn archetype:generate -DgroupId=com.example -DartifactId=demo \
  -DarchetypeArtifactId=maven-archetype-quickstart -DinteractiveMode=false

cd demo

# Introduce bug in main code
cat > src/main/java/com/example/App.java <<'EOF'
package com.example;

public class App {
    public static int add(int a, int b) {
        return a - b; // BUG: should be +
    }
}
EOF

cat > src/test/java/com/example/AppTest.java <<'EOF'
package com.example;

import org.junit.Test;
import static org.junit.Assert.*;

public class AppTest {
    @Test
    public void testAdd() {
        assertEquals(5, App.add(2, 3));
    }
}
EOF

mvn test

Expected: BUILD FAILURE with assertion error in output.

Save log:

mvn test 2>&1 | tee /tmp/java-maven.log

2. Fix with code-agent¶

source /path/to/ai-code-agent/.venv/bin/activate

code-agent run \
  "Fix failing AppTest. The add method in App.java returns wrong result. Run 'mvn test' until BUILD SUCCESS. Change only what is needed." \
  --verify-cmd "mvn test -q" \
  -w /tmp/java-demo/demo

3. Fix with bug-fix expert¶

code-agent experts run bug-fix \
  --log /tmp/java-maven.log \
  --verify-cmd "mvn test -q" \
  -w /tmp/java-demo/demo

Flags explained¶

Flag	Value	Why
`-w`	Maven module root (`pom.xml` here)	Agent edits `src/main` and `src/test`
`--verify-cmd`	`mvn test -q`	Must match CI — quiet Maven like Actions
`--log`	Maven surefire output	Failure class + line from log

Option B — Gradle project¶

1. Create project + failing test¶

mkdir -p /tmp/gradle-demo && cd /tmp/gradle-demo
git init

gradle init --type java-application --dsl kotlin --test-framework junit-jupiter --package com.example --project-name demo
cd demo

# Edit generated code to fail (similar App class + test)
./gradlew test

Save log:

./gradlew test 2>&1 | tee /tmp/java-gradle.log

2. Fix with code-agent¶

code-agent experts run bug-fix \
  --log /tmp/java-gradle.log \
  --verify-cmd "./gradlew test" \
  -w /tmp/gradle-demo/demo

Flag	Why
`--verify-cmd "./gradlew test"`	Gradle wrapper — same as CI
`-w`	Directory with `build.gradle.kts`

Add missing unit tests (coverage)¶

For Java coverage (JaCoCo), use verify command that includes coverage gate:

# Example — adjust to your pom.xml / build.gradle
mvn test jacoco:report 2>&1 | tee /tmp/java-cov.log

code-agent experts run bug-fix \
  --log /tmp/java-cov.log \
  --verify-cmd "mvn test jacoco:report" \
  -w /path/to/java-project

Agent adds tests under src/test/java/ for uncovered methods.

Open merge request¶

code-agent experts run bug-fix \
  --log /tmp/java-maven.log \
  --verify-cmd "mvn test -q" \
  -w /path/to/java-project \
  --publish \
  --base-branch main

Flag	Meaning
`--publish`	Creates branch + draft PR with fix
`--base-branch`	Target branch for MR

Requires gh auth login.

Common mistakes¶

Mistake	Fix
`-w` at wrong level	Must be folder with `pom.xml` or `build.gradle`
`mvn test` vs `mvn verify`	Use exact CI command in `--verify-cmd`
JDK not installed	Install JDK 17+; `java -version` must work
Mixing Maven and Gradle flags	Pick one build tool per project

← Back to Quick Start