samples: Add system tests to Translate sample.

translate/snippets/src/main/java/com/example/translate/QuickstartSample.java

@@ -26,7 +26,11 @@
 public class QuickstartSample {
   public static void main(String... args) throws Exception {
     // Instantiates a client
-    Translate translate = TranslateOptions.builder().apiKey("YOUR_API_KEY").build().service();
+    Translate translate =
+        TranslateOptions.builder()
+            .apiKey(args[0])  // .apiKey("YOUR_API_KEY")
+            .build()
+            .service();
 
     // The text to translate
     String text = "Hello, world!";

translate/snippets/src/test/java/com/example/translate/QuickstartSampleIT.java

@@ -0,0 +1,65 @@
+/*
+  Copyright 2016, Google, Inc.
+
+  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.example.translate;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+import java.io.ByteArrayOutputStream;
+import java.io.PrintStream;
+
+/**
+ * Tests for quickstart sample.
+ */
+@RunWith(JUnit4.class)
+@SuppressWarnings("checkstyle:abbreviationaswordinname")
+public class QuickstartSampleIT {
+  private ByteArrayOutputStream bout;
+  private PrintStream out;
+
+  @Before
+  public void setUp() {
+    bout = new ByteArrayOutputStream();
+    out = new PrintStream(bout);
+    System.setOut(out);
+  }
+
+  @After
+  public void tearDown() {
+    System.setOut(null);
+  }
+
+  @Test
+  public void testQuickstart() throws Exception {
+    // Arrange
+    String apiKey = System.getenv("GOOGLE_API_KEY");
+
+    // Act
+    QuickstartSample.main(apiKey);
+
+    // Assert
+    String got = bout.toString();
+    assertThat(got).contains("Text: Hello, world!");
+    assertThat(got).contains("Translation: ");
+  }
+}
+// [END datastore_quickstart]