Create CommandLineTestRule

base/test/android/javatests/src/org/chromium/base/test/util/CommandLineTestRule.java

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package org.chromium.base.test.util;
+
+import android.support.test.InstrumentationRegistry;
+
+import org.junit.rules.TestRule;
+import org.junit.runner.Description;
+import org.junit.runners.model.Statement;
+
+import org.chromium.base.test.SetUpTestRule;
+
+import java.util.Arrays;
+import java.util.HashSet;
+import java.util.Set;
+
+/**
+ * TestRule to used by JUnit4 style instrumentation test to set CommandLine flags.
+ *
+ * If you need to add CommandLine flag to your junit4 style instrumentation test, add this
+ * TestRule with the flag string you need. Remember to call setUp() before you launch
+ * the activity.
+ *
+ * <pre><code>
+ * public class ChromeActivityTest {
+ *     &#064;Rule CommandLineTestRule mCommandLineRule = new CommandLineTestRule().setFlags(...);
+ *     &#064;Rule ChromeActivityTestRule mActivityTestRule = new ChromeActivityTestRule();
+ *
+ *     &#064;Before
+ *     public void setUp() {
+ *       mCommandLineRule.setUp();
+ *       mActivityTestRule.launchActivity();
+ *     }
+ *
+ *     &#064;Test
+ *     public void test() {...}
+ * </code></pre>
+ *
+ */
+public final class CommandLineTestRule implements TestRule, SetUpTestRule<CommandLineTestRule> {
+    private Set<String> mFlagSet;
+    private boolean mShouldSetUp = false;
+
+    public CommandLineTestRule setFlags(String firstFlag, String... flags) {
+        mFlagSet = new HashSet<>();
+        mFlagSet.add(firstFlag);
+        mFlagSet.addAll(Arrays.asList(flags));
+        return this;
+    }
+
+    @Override
+    public CommandLineTestRule shouldSetUp(boolean shouldSetUp) {
+        mShouldSetUp = shouldSetUp;
+        return this;
+    }
+
+    @Override
+    public void setUp() {
+        CommandLineFlags.setUp(InstrumentationRegistry.getTargetContext(), mFlagSet);
+    }
+
+    @Override
+    public Statement apply(final Statement base, Description desc) {
+        return new SetUpStatement(base, this, mShouldSetUp);
+    }
+}