Add SingleRun, a safer mechanism than classSetUp

Change-Id: If7c8f42d9fbbfb012783d12587fbbfc8d0b01729

3 files changed, 81 insertions, 10 deletions

diff --git a/manualtest/src/com/google/android/droiddriver/manualtest/ManualTest.java b/manualtest/src/com/google/android/droiddriver/manualtest/ManualTest.java
index 238db2e..c1f3946 100644
--- a/manualtest/src/com/google/android/droiddriver/manualtest/ManualTest.java
+++ b/manualtest/src/com/google/android/droiddriver/manualtest/ManualTest.java
@@ -37,9 +37,4 @@ public class ManualTest extends BaseDroidDriverTest<Activity> {
     // assertEquals(password, driver.on(password_edit).getText());
     assertEquals(null, driver.on(password_edit).getText());
   }
-
-  @Override
-  protected final void classSetUp() {
-    DroidDrivers.init(DroidDrivers.newDriver(getInstrumentation()));
-  }
 }
diff --git a/src/com/google/android/droiddriver/helpers/BaseDroidDriverTest.java b/src/com/google/android/droiddriver/helpers/BaseDroidDriverTest.java
index 9905cf4..48113fd 100644
--- a/src/com/google/android/droiddriver/helpers/BaseDroidDriverTest.java
+++ b/src/com/google/android/droiddriver/helpers/BaseDroidDriverTest.java
@@ -17,6 +17,7 @@
 package com.google.android.droiddriver.helpers;
 
 import android.app.Activity;
+import android.app.Instrumentation;
 import android.content.Context;
 import android.os.Debug;
 import android.test.FlakyTest;
@@ -40,6 +41,30 @@ import java.lang.reflect.Modifier;
  */
 public abstract class BaseDroidDriverTest<T extends Activity> extends
     D2ActivityInstrumentationTestCase2<T> {
+  /**
+   * Calls {@link DroidDrivers#init} once and only once.
+   */
+  public static class DroidDriversInitializer extends SingleRun {
+    private static DroidDriversInitializer instance;
+    protected final Instrumentation instrumentation;
+
+    protected DroidDriversInitializer(Instrumentation instrumentation) {
+      this.instrumentation = instrumentation;
+    }
+
+    @Override
+    protected void run() {
+      DroidDrivers.init(DroidDrivers.newDriver(instrumentation));
+    }
+
+    public static synchronized DroidDriversInitializer get(Instrumentation instrumentation) {
+      if (instance == null) {
+        instance = new DroidDriversInitializer(instrumentation);
+      }
+      return instance;
+    }
+  }
+
   private static boolean classSetUpDone = false;
   // In case of device-wide fatal errors, e.g. OOME, the remaining tests will
   // fail and the messages will not help, so skip them.
@@ -86,12 +111,17 @@ public abstract class BaseDroidDriverTest<T extends Activity> extends
   }
 
   /**
-   * Initializes test fixture once for all tests extending this class. Typically
-   * you call {@link DroidDrivers#init} with an appropriate instance. If an
-   * InstrumentationDriver is used, this is a good place to call
-   * {@link com.google.android.droiddriver.instrumentation.ViewElement#overrideClassName}
+   * Initializes test fixture once for all tests extending this class. This may have unexpected
+   * behavior - if multiple subclasses override this method, only the override is executed. The
+   * other overrides are silently ignored. You can either use {@link SingleRun} in {@link #setUp},
+   * or override this method, which is a simpler alternative with the aforementioned catch.
+   * <p/>
+   * If an InstrumentationDriver is used, this is a good place to call {@link
+   * com.google.android.droiddriver.instrumentation.ViewElement#overrideClassName}
    */
-  protected abstract void classSetUp();
+  protected void classSetUp() {
+    DroidDriversInitializer.get(getInstrumentation()).singleRun();
+  }
 
   protected boolean reportSkippedAsFailed() {
     return false;
diff --git a/src/com/google/android/droiddriver/helpers/SingleRun.java b/src/com/google/android/droiddriver/helpers/SingleRun.java
new file mode 100644
index 0000000..d11e1b0
--- /dev/null
+++ b/src/com/google/android/droiddriver/helpers/SingleRun.java
@@ -0,0 +1,46 @@
+/*
+ * Copyright (C) 2015 DroidDriver committers
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.android.droiddriver.helpers;
+
+import java.util.concurrent.atomic.AtomicBoolean;
+
+/**
+ * Base class for an action that should run only once no matter how many times the method {@link
+ * #singleRun()} is called upon an instance. Typically it is used on a singleton to achieve once for
+ * a class effect.
+ */
+public abstract class SingleRun {
+  private AtomicBoolean hasRun = new AtomicBoolean();
+
+  /**
+   * Calls {@link #run()} if it is the first time this method is called upon this instance.
+   *
+   * @return true if this is the first time it is called, otherwise false
+   */
+  public boolean singleRun() {
+    if (hasRun.compareAndSet(false, true)) {
+      run();
+      return true;
+    }
+    return false;
+  }
+
+  /**
+   * Takes the action that should run only once.
+   */
+  protected abstract void run();
+}