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Diff coverage gradle plugin

Diff coverage is JaCoCo extension that computes code coverage of new/modified code based on a provided diff. The diff content can be provided via path to patch file, URL or using embedded git(see parameters description).

Why should I use it?

• forces each developer to be responsible for its own code quality(see diffCoverage task)
• helps to increase total code coverage(especially useful for old legacy projects)
• reduces time of code review(you don't need to waste your time to track what code is covered)

Installation

Add plugin dependency

buildscript {
    repositories {
        maven { url 'https://jitpack.io' }
    }
    dependencies {
        classpath 'com.github.form-com.diff-coverage-gradle:diff-coverage:0.9.4'
    }
}

buildscript {
    repositories {
        maven("https://jitpack.io")
    }
    dependencies {
        classpath("com.github.form-com.diff-coverage-gradle:diff-coverage:0.9.4")
    }
}

Apply JaCoCo and Diff Coverage plugins

• JaCoCo is used to collect coverage data
• Diff Coverage is used to generate diff report

apply plugin: 'jacoco'
apply plugin: 'com.form.diff-coverage'

plugins {
    jacoco
}
apply(plugin = "com.form.diff-coverage")

Configuration

diffCoverageReport {
    diffSource.file = ${PATH_TO_DIFF_FILE} 

    violationRules.failIfCoverageLessThan 0.9
    
    reports {
        html = true
    }
}

configure<com.form.coverage.gradle.ChangesetCoverageConfiguration> {
    diffSource.file = ${PATH_TO_DIFF_FILE}

    violationRules.failIfCoverageLessThan(0.9)
    reports {
        html = true
    }
}

buildscript {
    repositories {
        maven { url 'https://jitpack.io' }
    }
    dependencies {
        classpath 'com.github.form-com.diff-coverage-gradle:diff-coverage:0.9.4'
    }
}

apply plugin: 'java'
apply plugin: 'jacoco'
apply plugin: 'com.form.diff-coverage'

diffCoverageReport {
    diffSource {
        git.compareWith 'refs/remotes/origin/develop'
    }

    violationRules.failIfCoverageLessThan 0.9

    reports {
        html = true
        xml = true
        csv = true
    }
}
diffCoverage.dependsOn += check

Execute

./gradlew check diffCoverage

Parameters description

diffCoverageReport {
    diffSource { // Required. Only one of `file`, `url` or git must be spesified
        file = 'path/to/file.diff' //  Path to diff file 
        url = 'http://domain.com/file.diff' // URL to retrieve diff by
        git.compareWith 'refs/remotes/origin/develop' // Compares current HEAD and all uncommited with provided branch, revision or tag 
    }
    jacocoExecFiles = files('/path/to/jacoco/exec/file.exec') // Required. By default exec files are taken from jacocoTestReport configuration if any
    srcDirs = files('/path/to/sources')  // Required. By default sources are taken from jacocoTestReport configuration if any
    classesDirs = files('/path/to/compiled/classes') // Required. By default classes are taken from jacocoTestReport configuration if any

    reports {
        html = true // Optional. default `false`
        xml = true // Optional. default `false`
        csv = true // Optional. default `false`
        reportDir = 'dir/to/store/reports' // Optional. Default 'build/reports/jacoco/diffCoverage'
    }

    violationRules.failIfCoverageLessThan 0.9 // Optional. The function sets all coverage metrics to a single value, sets failOnViolation to true
    
    // configuration below is equivalent to the configuration above
    violationRules {        
        minBranches = 0.9 // Optional. Default `0.0`
        minLines = 0.9 // Optional. Default `0.0`
        minInstructions = 0.9 // Optional. Default `0.0`
        failOnViolation = true // Optional. Default `false`
    }
}

Gradle task description

The plugin adds a task diffCoverage that has no dependencies

• loads code coverage data specified by diffCoverageReport.jacocoExecFiles

• analyzes the coverage data and filters according to diffSource.url/diffSource.file

• generates html report(if enabled: reports.html = true) to directory reports.baseReportsDir

• checks coverage ratio if violationRules is specified.

  Violations check is enabled if any of minBranches, minLines, minInstructions is greater than 0.0.

  Fails the execution if the violation check is enabled and violationRules.failOnViolation = true

Violations check output example

Passed:

>Task :diffCoverage

Fail on violations: true. Found violations: 0.

Failed:

> Task :diffCoverage FAILED

Fail on violations: true. Found violations: 2.

FAILURE: Build failed with an exception.

...

> java.lang.Exception: Rule violated for bundle diff-coverage-gradle: instructions covered ratio is 0.5, but expected minimum is 0.9

Rule violated for bundle diff-coverage-gradle: lines covered ratio is 0.0, but expected minimum is 0.9

HTML report example

Diff Coverage plugin generates standard JaCoCo HTML report, but highlights only modified code

JaCoCo HTML report