test(android, jacoco): configure app and modules for offline coverage instrumentation

the resources file is a special trick so the jacoco offline agent does not crash
jacoco/jacoco#968

Author: mikehardy

tests/android/app/build.gradle

@@ -74,6 +74,10 @@ android {
   }
 
   buildTypes {
+    debug {
+      debuggable true
+      testCoverageEnabled true
+    }
     release {
       minifyEnabled true
       proguardFiles getDefaultProguardFile("proguard-android.txt"), "proguard-rules.pro"
@@ -82,6 +86,12 @@ android {
     }
   }
 
+  testOptions {
+    unitTests {
+      includeAndroidResources = true
+    }
+  }
+
   compileOptions {
     sourceCompatibility 1.8
     targetCompatibility 1.8

tests/android/app/src/debug/resources/jacoco-agent.properties

@@ -0,0 +1 @@
+ output=none

tests/android/build.gradle

@@ -80,9 +80,17 @@ subprojects {
         }
       }
     }
-    if (project.name.contains('firebase')
+
+    // Configure testing settings - if set in module build.gradle files they affect library consumers
+    if (project.name.contains("react-native-firebase")
       && project.hasProperty('android')) {
       android {
+        // Instrument all our modules for coverage generation
+        buildTypes.debug.testCoverageEnabled true
+        jacoco.version '0.8.7'
+        testOptions.unitTests.includeAndroidResources = true
+
+        // Make sure our project are run through basic lint checks
         lintOptions {
           abortOnError = true
           warningsAsErrors false