fixes translate sample README and tests (GoogleCloudPlatform#849)

Author: bshaffer

translate/README.md

@@ -13,8 +13,13 @@ https://cloud.google.com/translate/).
 ## Build and Run
 1.  **Enable APIs** - [Enable the Translate API](https://console.cloud.google.com/flows/enableapi?apiid=translate)
     and create a new project or select an existing project.
-2.  **Download The Credentials** - Click "Go to credentials" after enabling the APIs. Click "Create Credentials"
-    and select "API key". Copy the API key.
+2.  **Download The Credentials** - Configure your project using [Application Default Credentials][adc].
+    Click "Go to credentials" after enabling the APIs. Click "Create Credentials"
+    and select "Service Account Credentials" and download the credentials file. Then set the path to
+    this file to the environment variable `GOOGLE_APPLICATION_CREDENTIALS`:
+```
+    $ export GOOGLE_APPLICATION_CREDENTIALS=/path/to/credentials.json
+```
 3.  **Clone the repo** and cd into this directory
 ```
     $ git clone https://github.com/GoogleCloudPlatform/php-docs-samples
@@ -58,3 +63,5 @@ Available commands:
 ## Licensing
 
 * See [LICENSE](../LICENSE)
+
+[adc]: https://cloud.google.com/docs/authentication/production#obtaining_and_providing_service_account_credentials_manually

translate/test/quickstartTest.php

@@ -21,6 +21,9 @@ public function testQuickstart()
         if (!$projectId = getenv('GOOGLE_PROJECT_ID')) {
             $this->markTestSkipped('GOOGLE_PROJECT_ID must be set.');
         }
+        if (!getenv('GOOGLE_APPLICATION_CREDENTIALS')) {
+            $this->markTestSkipped('GOOGLE_APPLICATION_CREDENTIALS must be set.');
+        }
 
         $file = sys_get_temp_dir() . '/translate_quickstart.php';
         $contents = file_get_contents(__DIR__ . '/../quickstart.php');