Commit Level Coverage Reporting

What is it?

This enables coverage reporting showing lines not covered on each commit

Where is it?

https://github.com/juliangamble/commit-level-coverage-report

Is there an example project?

https://github.com/juliangamble/jacoco-example-project

Why you would use this

[Workplace with a million line codebase and 100s of developers working on it.]

Tech Lead: “We really want to get the coverage up on this codebase – more tests will give us more feedback about the code.”

Developer: “Well that’s lovely, but I really need to ship my feature – I’ll make sure my stuff is covered as best I can.”

Tech Lead: “Ok – how much coverage are you aiming for?”

Developer: “I’ll make sure the lines I touch have coverage.”

Tech Lead: “Ok – how will you measure that?” ….

Now obviously:

(a) this codebase is a candidate for modularisation and

(b) sonar does give you feedback on coverage at a commit level – but sonar doesn’t give you a way to know what the commit-level coverage is prior to pushing your changes. ie – if you’ve missed some coverage on the lines you’ve changed – there isn’t a way to know before pushing.

This change is trying to solve the problem of knowing “for the lines I have touched – what coverage have I got? What lines have I missed?”

How to setup and use in your project

Add the following into your pom.xml

<project>
    <build>
        <plugins>
            <plugin>
                <groupId>com.github.juliangamble</groupId>
                <artifactId>commit-level-coverage-report</artifactId>
                <version>1.0</version>
                <executions>
                    <execution>
                        <id>post-unit-test2</id>
                        <phase>test</phase>
                        <goals>
                            <goal>report-on-commit-coverage</goal>
                        </goals>
                        <configuration>
                            <!-- Optional - sets the path to the file which contains the execution data. -->
                            <!-- <dataFile>${project.build.directory}/coverage-reports/jacoco.exec</dataFile> -->
                            <!-- Sets the output directory for the code coverage report. -->
                            <outputDirectory>${project.reporting.outputDirectory}/</outputDirectory>
                            <daysBackToCheck>100</daysBackToCheck>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>
</project>

Then run this:

mvn clean test

Example Result

----
Commit: caaa32f8c8eff580b4760f60dbf021d6e03935c3 - Sun Jul 16 20:48:50 AEST 2017 - Julian Gamble - [dev] first drop

source file name: /com/machiavellian/MyApplication.java
Intersection of line changes with coverage (lines we care about): 4
covered lines: 3
Coverage for commit: 75%
Lines not covered: 1
src/main/java/com/machiavellian/MyApplication.java:11         return firstArg - secondArg;

----
Commit: 57bfb7956b501afca5fc101753d6e284d448f4ce - Sun Jul 16 20:53:59 AEST 2017 - Julian Gamble - [dev] adding new method

Intersection of line changes with coverage (lines we care about): 1
covered lines: 1
Coverage for commit: 100%
Lines not covered: 0
----
Commit: acf35680891d1f853a226035981c1ac18d9f50a2 - Sun Jul 16 20:55:58 AEST 2017 - Julian Gamble - [dev] adding coverage

Intersection of line changes with coverage (lines we care about): 0
covered lines: 0
Coverage for commit: 0%
Lines not covered: 0
----
Commit: 9c42a1ab1e8db57e31e17837120da6dc257dbb72 - Sun Jul 16 20:56:23 AEST 2017 - Julian Gamble - [dev] adding divide method

Intersection of line changes with coverage (lines we care about): 1
covered lines: 0
Coverage for commit: 0%
Lines not covered: 1
src/main/java/com/machiavellian/MyApplication.java:19         return firstArg / secondArg;

----

Result File Location

target/site/coverage-per-commit.txt

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