Add code coverage reports

README.md

@@ -94,6 +94,21 @@ You can also run the benchmarks:
 
     ./gradlew jmh
 
+### Code Coverage
+
+The "Jacoco" coverage is enabled by default for the main published modules as well as the special 
+"tests" module. Coverage is generated for each of the main projects separately and available by
+running
+
+    ./gradlew jacocoTestReport
+
+To see an aggregated coverage report for everything, which is probably what you want, run
+
+    ./gradlew testCodeCoverageReport
+
+The result is in:
+    ./tests/build/reports/jacoco/testCodeCoverageReport/html
+
 ## Releasing and publishing new version
 
 1. Ensure all tests are passing

buildSrc/src/main/groovy/rhino.library-conventions.gradle

@@ -3,6 +3,7 @@ plugins {
     id 'com.github.spotbugs'
     id 'maven-publish'
     id 'checkstyle'
+    id 'jacoco'
 }
 
 import com.github.spotbugs.snom.Confidence
@@ -41,6 +42,14 @@ spotbugsMain {
     }
 }
 
+jacocoTestReport {
+    reports {
+        xml.required = false
+        csv.required = false
+        html.outputLocation = layout.buildDirectory.dir('reports/jacoco')
+    }
+}
+
 task javadocJar(type: Jar) {
     archiveClassifier = 'javadoc'
     from javadoc

tests/build.gradle

@@ -1,5 +1,7 @@
 plugins {
     id 'rhino.java-conventions'
+    id 'jacoco'
+    id 'jacoco-report-aggregation'
 }
 
 dependencies {
@@ -45,4 +47,12 @@ test {
     if (System.getProperty('updateTest262properties') != null) {
         systemProperty 'updateTest262properties', System.getProperty('updateTest262properties')
     }
-}
+}
+
+jacocoTestReport {
+    reports {
+        xml.required = false
+        csv.required = false
+        html.outputLocation = layout.buildDirectory.dir('reports/jacoco')
+    }
+}