[js] Extend firefox.Options for easily configuring Firefox to run in headless

mode.

Fixes #4591

Author: jleyba

javascript/node/selenium-webdriver/CHANGES.md

@@ -8,7 +8,10 @@
 
 ### API Changes
 
-* Added `selenium-webdriver/firefox.Options#addArguments()`
+* Added new methods to `selenium-webdriver/firefox.Options`:
+  - addArguments()
+  - headless()
+  - windowSize()
 * Deprecated `selenium-webdriver/firefox/binary.Binary`
 * Removed `selenium-webdriver/firefox.Options#useGeckoDriver()`
 * Removed the unused `selenium-webdriver/firefox/profile.decode()`

javascript/node/selenium-webdriver/example/chrome_headless.js renamed to javascript/node/selenium-webdriver/example/headless.js

@@ -16,17 +16,23 @@
 // under the License.
 
 /**
- * @fileoverview An example of running Chrome in headless mode.
+ * @fileoverview An example of running Chrome or Firefox in headless mode.
  *
- * Before running this script, ensure you have Chrome 59+ installed and that
+ * To run with Chrome, ensure you have Chrome 59+ installed and that
  * chromedriver 2.30+ is present on your system PATH:
  * <https://sites.google.com/a/chromium.org/chromedriver/downloads>
  *
- * Usage:
- *   node selenium-webdriver/example/chrome_headless.js
+ *     SELENIUM_BROWSER=chrome node selenium-webdriver/example/headless.js
+ *
+ * To run with Firefox, ensure you have Firefox 57+ installed and that
+ * geckodriver 0.19.0+ is present on your system PATH:
+ * <https://github.com/mozilla/geckodriver/releases>
+ *
+ *     SELENIUM_BROWSER=firefox node selenium-webdriver/example/headless.js
  */
 
 const chrome = require('../chrome');
+const firefox = require('../firefox');
 const {Builder, By, Key, until} = require('..');
 
 const width = 640;
@@ -36,6 +42,8 @@ let driver = new Builder()
     .forBrowser('chrome')
     .setChromeOptions(
         new chrome.Options().headless().windowSize({width, height}))
+    .setFirefoxOptions(
+        new firefox.Options().headless().windowSize({width, height}))
     .build();
 
 driver.get('http://www.google.com/ncr')

javascript/node/selenium-webdriver/firefox/index.js

@@ -170,6 +170,35 @@ class Options {
     return this;
   }
 
+  /**
+   * Configures the geckodriver to start Firefox in headless mode.
+   *
+   * @return {!Options} A self reference.
+   */
+  headless() {
+    return this.addArguments('-headless');
+  }
+
+  /**
+   * Sets the initial window size when running in
+   * {@linkplain #headless headless} mode.
+   *
+   * @param {{width: number, height: number}} size The desired window size.
+   * @return {!Options} A self reference.
+   * @throws {TypeError} if width or height is unspecified, not a number, or
+   *     less than or equal to 0.
+   */
+  windowSize({width, height}) {
+    function checkArg(arg) {
+      if (typeof arg !== 'number' || arg <= 0) {
+        throw TypeError('Arguments must be {width, height} with numbers > 0');
+      }
+    }
+    checkArg(width);
+    checkArg(height);
+    return this.addArguments(`--window-size=${width},${height}`);
+  }
+
   /**
    * Sets the profile to use. The profile may be specified as a
    * {@link Profile} object or as the path to an existing Firefox profile to use