Multi-Module Projects

Delta Coverage automatically discovers and aggregates coverage across all modules in multi-module Gradle builds.

How It Works

When applied to the root project, the plugin:

1. Scans all subprojects for test tasks
2. Creates a view for each test task found
3. Creates an aggregated view combining all coverage data

Example Structure

my-project/
├── build.gradle.kts       # Apply plugin here
├── app/
│   └── src/test/          # test task → "test" view
├── core/
│   └── src/test/          # test task → "test" view
└── api/
    └── src/test/          # test task → "test" view

Configuration

Apply the plugin to the root project only:

// root build.gradle.kts
plugins {
    id("io.github.gw-kit.delta-coverage") version "3.6.0"
}

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

    reportViews {
        val test by getting {
            violationRules.failIfCoverageLessThan(0.9)
        }
    }
}

Don't apply to subprojects

The plugin should only be applied to the root project. It automatically handles subprojects.

Aggregated View

When the plugin discovers 2+ views, it creates an aggregated view that combines coverage data from all views across all modules:

./gradlew deltaCoverageAggregated

This produces a single report showing coverage across the entire project.

Configure Aggregated View

reportViews {
    val aggregated by getting {
        violationRules.failIfCoverageLessThan(0.85)
    }
}

Running Coverage Tasks

# Run all views
./gradlew deltaCoverage

# Run only the aggregated view
./gradlew deltaCoverageAggregated

# Run only the test view (all modules' unit tests)
./gradlew deltaCoverageTest

Multiple Test Types

If modules have different test tasks (e.g., test, integrationTest):

my-project/
├── app/
│   ├── src/test/              # unit tests
│   └── src/integrationTest/   # integration tests
└── core/
    └── src/test/              # unit tests only

The plugin creates views for each unique test task:

• test - unit tests from all modules
• integrationTest - integration tests from app
• aggregated - everything combined

Excluding Modules

Exclude a module from coverage:

// In the subproject's build.gradle.kts
tasks.withType<Test> {
    extensions.configure<JacocoTaskExtension> {
        isEnabled = false
    }
}

Or exclude specific classes:

// Root build.gradle.kts
configure<io.github.surpsg.deltacoverage.gradle.DeltaCoverageConfiguration> {
    excludeClasses.value(
        listOf("**/legacy-module/**/*.*")
    )
}

Troubleshooting

Module coverage not included

1. Verify the module has a test task
2. Check that JaCoCo/CoverJet is applied (auto-applied by default)
3. Run with -PexplainOnly to see discovered modules

Aggregated view is missing

The aggregated view is only created when 2+ views exist. If all modules only have the test task, there is a single view — declare custom views to get aggregation.

Different thresholds for different code

Declare custom views with class filters:

reportViews {
    view("coreTests") {
        includeClasses.value(listOf("**/core/**/*.class"))
        violationRules.failIfCoverageLessThan(0.95)  // Stricter
    }

    view("legacyTests") {
        includeClasses.value(listOf("**/legacy/**/*.class"))
        violationRules.failIfCoverageLessThan(0.5)  // More lenient
    }
}