Make a global test task

Change-Id: I9cd6226cf3e724582ae479cc0bf016098d1b89ee

Author: samtstern

.travis.yml

@@ -16,4 +16,4 @@ android:
     - 'android-sdk-license-.+'
     - 'google-gdk-license-.+'
 script:
-  - ./gradlew clean test :library:prepareArtifacts
+  - ./gradlew clean :library:testAll :library:prepareArtifacts

library/build.gradle

@@ -56,6 +56,15 @@ def bintrayUploadTasks() {
     }.toArray()
 }
 
+/**
+ * Returns a list of tasks names to test submodules.
+ */
+def testTasks() {
+    return project.ext.submodules.collect { name ->
+        ":${name}:test"
+    }.toArray()
+}
+
 /**
  * Prepare artifacts for this an all sub-projects.
  */
@@ -93,3 +102,9 @@ task bintrayUploadAll(dependsOn: [
         bintrayUploadTasks()]) {
 
 }
+
+/**
+ * Test all submodules.
+ */
+task testAll(dependsOn: [testTasks()]) {
+}