Add code coverage report to build

.github/workflows/build.yml

@@ -97,3 +97,11 @@ jobs:
           name: test-reports-jdk-${{ matrix.java_version }}
           path: |
             **/build/reports/tests/test
+
+      - name : Publish code coverage report
+        if: success()
+        uses : actions/upload-artifact@v4
+        with :
+          name : code-coverage-reports-jdk-${{ matrix.java_version }}
+          path : |
+            **/build/reports/jacoco/test

build.gradle

@@ -8,6 +8,7 @@ plugins {
     id "io.micronaut.minimal.application" version "3.7.0"
     id "com.google.cloud.tools.jib" version "3.4.2"
     id 'org.asciidoctor.jvm.convert' version '3.3.2'
+    id 'jacoco'
 }
 
 String gitVersion() {
@@ -183,3 +184,23 @@ task buildInfo { doLast {
 buildInfo.dependsOn processResources
 compileGroovy.dependsOn buildInfo
 
+jacoco {
+    toolVersion '0.8.12'
+}
+/**
+ * Code coverage with JaCoCo.
+ * See: https://www.jacoco.org/; https://docs.gradle.org/current/userguide/jacoco_plugin.html
+ */
+// Code coverage report is always generated after tests run
+test { finalizedBy jacocoTestReport }
+jacocoTestReport {
+    // Tests are required to run before generating the code coverage report
+    dependsOn test
+    // Remove closure classes from the report, as they are already covered by the enclosing class coverage stats adding only noise.
+    // See: https://stackoverflow.com/questions/39453696
+    afterEvaluate {
+        classDirectories.setFrom(files(classDirectories.files.collect { dir ->
+            fileTree(dir: dir, excludes: ['**/*$*_closure*'])
+        }))
+    }
+}