Added project property to enable test coverage.

gradle/emma.gradle

@@ -29,6 +29,7 @@ task emmaInstrument {
 
 // Modify test tasks in the project to generate coverage data
 afterEvaluate {
+    if (project.hasProperty('coverage') && ['on','true'].contains(project.properties.coverage)) {
         tasks.withType(Test.class).each { task ->
             task.dependsOn emmaInstrument
             task.configure() {
@@ -39,6 +40,7 @@ afterEvaluate {
             }
         }
     }
+}
 
 if (rootProject.getTasksByName('coverageReport', false).isEmpty()) {
     rootProject.task('coverageReport') << {