diff-coverage-maven-plugin

Diff coverage maven plugin builds JaCoCo compatible code coverage report of new and modified code based on a provided diff.

The plugin is able to check and fail a build if code coverage rules are not met.

How it works

Diff coverage works in tandem with JaCoCo and requires JaCoCo to be applied to a project as well. The plugin does the next steps:

• analyzes coverage data('.exec' files generated by JaCoCo)
• cuts off all code coverage data that wasn't modified
• checks violation rules if any are set up
• builds diff coverage HTML report. See HTML report example

Install plugin

<build>
    <plugins>
        <plugin> <!-- Make sure JaCoCo plugin is applied -->
            <groupId>org.jacoco</groupId>
            <artifactId>jacoco-maven-plugin</artifactId>
            <version>0.8.7</version>
        </plugin>
        <plugin>
            <groupId>com.github.surpsg</groupId>
            <artifactId>diff-coverage-maven-plugin</artifactId>
            <version>0.2.1</version>
            <configuration>
                <!-- Required. diff content source. only one of file, URL or Git is allowed -->
                <diffSource>
                    <!-- path to diff file -->
                    <file>path/to/diffFile</file>
                    
                    <!-- branch, revision or tag -->
                    <git>HEAD</git> <!-- compares current HEAD and all uncommited with this <git> -->
                
                    <!-- URL to get diff content by. Used GET method -->
                    <url>http://url.com</url>
                </diffSource>
                
                <!-- Optional -->
                <violations> 
                    <!-- Default 'false'. Fail build if violation rules weren't met  -->
                    <failOnViolation>true</failOnViolation>

                    <!-- Sets min coverage rule for: instructions, lines, branches -->
                    <minCoverage>0.7</minCoverage>
                    
                    <!-- Each rule could be configured separately -->
                    <!-- Default '0.0'. If value is '0.0' then the rule is disabled -->
                    <minLines>0.1</minLines>
                    <minBranches>0.7</minBranches>
                    <minInstructions>1.0</minInstructions>
                </violations>

                <!-- Optional. Exec files include pattern. By default 'build/jacoco.exec' file is used -->
                <dataFileIncludes>**/custom/exec/location/*.exec</dataFileIncludes>
                
                <!-- Optional. Exec files exclude pattern -->
                <dataFileExcludes>**/custom/**/exclude/*.exec</dataFileExcludes>
                
                <!-- Optional. Ant patterns by which we include classes for coverage report. -->
                <includes>
                    <include>**/package/**</include>
                    <include>**/ClassNamePrefix*</include>
                </includes>
                <!-- Optional. Ant patterns by which we exclude classes from coverage report. -->
                <excludes>
                    <exclude>**/exclude/**/ClassName.class</exclude>
                </excludes>
                <!-- If neither <includes> nor <excludes> are specified then we pass all classes for coverage report -->
                
            </configuration>
            <executions>
                <execution>
                    <goals>
                        <goal>diffCoverage</goal>
                    </goals>
                </execution>
            </executions>
        </plugin>
    </plugins>
</build>

Maven goal description

Diff Coverage Maven plugin has a single goal diffCoverage that is bind to verify phase

# run tests and build diff coverage report
mvn clean verify

# Invoke the goal explicitly.
# It depends on `test` phase, make sure it's called when coverage data(*.exec files) already generated.  
mvn clean test diff-coverage:diffCoverage

Report example

Maven output on failed violation rules:

[INFO] File src/main/kotlin/org/example/Hello.kt has 5 modified lines
[INFO] New violation: Rule violated for bundle untitled: instructions covered ratio is 0.4, but expected minimum is 0.7
[INFO] New violation: Rule violated for bundle untitled: lines covered ratio is 0.6, but expected minimum is 0.7
[WARNING] Fail on violations: true. Found violations: 2.
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  9.919 s
[INFO] Finished at: 2020-07-06T00:56:33+03:00
[INFO] ------------------------------------------------------------------------
[ERROR] Rule violated for bundle TestProj: instructions covered ratio is 0.4, but expected minimum is 0.7
[ERROR] Rule violated for bundle TestProj: lines covered ratio is 0.6, but expected minimum is 0.7

The plugin creates JaCoCo like HTML, XML and CSV reports in directory target/site/diffCoverage/.

JaCoCo HTML report