Move example plugin out of core

Summary:
We should not ship this as part of our distribution.
Just meant we had to bifurcate our unit tests which
is a bit awkward, but it works now.

Reviewed By: jknoxville

Differential Revision: D15146980

fbshipit-source-id: 496b000630bbfcaa663cddacb00550e1499a1279

android/sample/build.gradle

@@ -23,6 +23,12 @@ android {
         main {
             manifest.srcFile './AndroidManifest.xml'
         }
+
+        test {
+            java {
+                exclude 'com/facebook/flipper/plugins/facebook/**'
+            }
+        }
     }
 
     compileOptions {
@@ -52,5 +58,11 @@ dependencies {
     androidTestImplementation deps.testCore
     androidTestImplementation deps.testRules
 
+    // Unit tests
+    testImplementation deps.mockito
+    testImplementation deps.robolectric
+    testImplementation deps.hamcrest
+    testImplementation deps.junit
+
     implementation project(':android')
 }

android/sample/src/test/java/com/facebook/flipper/plugins/example/ExampleFlipperPluginTest.java

@@ -16,8 +16,10 @@ import com.facebook.flipper.testing.FlipperResponderMock;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.robolectric.RobolectricTestRunner;
+import org.robolectric.annotation.Config;
 
 @RunWith(RobolectricTestRunner.class)
+@Config(application = TestApplication.class)
 public class ExampleFlipperPluginTest {
 
   @Test

android/sample/src/test/java/com/facebook/flipper/plugins/example/TestApplication.java

@@ -0,0 +1,12 @@
+/*
+ *  Copyright (c) 2018-present, Facebook, Inc.
+ *
+ *  This source code is licensed under the MIT license found in the LICENSE
+ *  file in the root directory of this source tree.
+ *
+ */
+package com.facebook.flipper.plugins.example;
+
+import android.app.Application;
+
+public class TestApplication extends Application {}