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Quick Start

Get Delta Coverage running in 3 steps.

Prerequisites

  • Gradle 7.6.4 or newer
  • JVM 17 or newer
  • A git repository with tests
  • Gradle 7.6.4 or newer
  • JVM 17 or newer
  • A git repository with tests
  • JVM 17 or newer
  • Coverage binary files (e.g., .exec from JaCoCo)
  • Compiled class files
  • A diff file (unified diff format)

Step 1: Install

Add the Delta Coverage plugin to your root project's build.gradle.kts:

plugins {
    id("io.github.gw-kit.delta-coverage") version "3.6.0"
}

Add the Delta Coverage plugin to your root project's build.gradle:

plugins {
    id 'io.github.gw-kit.delta-coverage' version '3.6.0'
}

Download the CLI JAR:

curl -L -o delta-coverage-cli.jar \
  https://repo1.maven.org/maven2/io/github/gw-kit/delta-coverage-cli/3.6.0/delta-coverage-cli-3.6.0.jar

Root project only

The Gradle plugin must be applied to the root project. It automatically discovers all subprojects with tests.

Step 2: Configure Diff Source

Tell Delta Coverage what to compare against. The most common setup compares with your main branch:

configure<io.github.surpsg.deltacoverage.gradle.DeltaCoverageConfiguration> {
    diffSource.git.compareWith("refs/remotes/origin/main")
}

deltaCoverageReport {
    diffSource.git.compareWith('refs/remotes/origin/main')
}

Generate a diff file from git:

git diff origin/main...HEAD > changes.diff

Step 3: Run Coverage

Run your tests and generate the delta coverage report:

./gradlew test deltaCoverage

Run your tests and generate the delta coverage report:

./gradlew test deltaCoverage

Run the CLI with your coverage data:

java -jar delta-coverage-cli.jar \
  --engine JACOCO \
  --diff-file changes.diff \
  --coverage-binary build/jacoco/test.exec \
  --classes build/classes/java/main \
  --sources src/main/java \
  --html --console

Expected Output

The console will show a coverage summary:

+----------------------+----------+----------+--------+
| [test] Delta Coverage Stats                         |
+----------------------+----------+----------+--------+
| Class                | Lines    | Branches | Instr. |
+----------------------+----------+----------+--------|
| com.example.MyClass  | 85.71%   | 75%      | 88.24% |
+----------------------+----------+----------+--------+
| Total                | 85.71%   | 75%      | 88.24% |
+----------------------+----------+----------+--------+

HTML reports are generated in build/reports/coverage-reports/delta-coverage/.

What Just Happened?

  1. Test Discovery — The plugin found your test tasks automatically
  2. Coverage Collection — JaCoCo collected coverage data during tests
  3. Diff Analysis — Git diff was computed against origin/main
  4. Filtered Report — Coverage was filtered to show only changed lines
  1. Test Discovery — The plugin found your test tasks automatically
  2. Coverage Collection — JaCoCo collected coverage data during tests
  3. Diff Analysis — Git diff was computed against origin/main
  4. Filtered Report — Coverage was filtered to show only changed lines
  1. Diff Parsing — The CLI read your diff file to identify changed lines
  2. Coverage Loading — Coverage binary files were loaded and analyzed
  3. Class Matching — Changed files were matched to compiled class files
  4. Filtered Report — Coverage was filtered to show only changed lines

Next Steps