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Selenium WebDriver Recipes in Node.js

Miscellaneous Techniques

Explore various debugging techniques for Selenium WebDriver test scripts, including taking screenshots on failures, keeping browsers open for inspection, and running selected test steps against an existing browser session to speed up troubleshooting and enhance test reliability.

We'll cover the following...

Take a screenshot

Another way of debugging is to take a screenshot of the current browser window when an error/failure occurs. Selenium supports this in a very easy way:

var fs = require('fs');    
driver.takeScreenshot().then(function(data) {
  // Base64 encoded png
  fs.writeFileSync(__dirname + "/tmp/screenshot1.png", data, 'base64');      
});

However, there is one problem with the above script. When the above script runs for the second time, it will return an error The file already exists. So, a simple workaround is to write a file with the timestamped file name as:

Javascript (babel-node)
// save to timestamped file, e.g. screenshot-12070944.png
Date.prototype.yyyymmdd = function() {
  var mm = this.getMonth() + 1; // getMonth() is zero-based
  var dd = this.getDate();
  return [this.getFullYear(), !mm[1] && '0', mm, !dd[1] && '0', dd].join('');
};
function writeScreenshot(data) {
  name = new Date().yyyymmdd() + ".png";
  var screenshotPath = __dirname + "/tmp/";  
  var fs = require('fs');      
  fs.writeFileSync(screenshotPath + name, data, 'base64');
};
test.it("Take screenshot saved to timestamped file", function() {
  driver.takeScreenshot().then(function(data) {
    writeScreenshot(data);
  });
});

Testing the recipe

Practice the screenshot code given in the recipe above. To execute the example test script, click the Run button.


var assert = require('assert');
var webdriver = require('selenium-webdriver'),
              By = webdriver.By,
              until = webdriver.until;
var test = require('selenium-webdriver/testing');  
var driver;
const timeOut = 15000;            



const chromeCapabilities = webdriver.Capabilities.chrome();
chromeCapabilities.set('chromeOptions', {args: ['--headless', '--disable-gpu','--no-sandbox','--disable-dev-shm-usage']});




var site_root_url = "file://" + __dirname + "/../../site"

String.prototype.contains = function(it) { return this.indexOf(it) != -1; };

test.describe('Debug', function() {

  test.before(function() {
    this.timeout(timeOut);
      driver = new webdriver.Builder()
      .forBrowser('chrome')
      .withCapabilities(chromeCapabilities)
      .build();
  });
  
  test.after(function() {
    driver.quit();
  });

  test.beforeEach(function() {
    // runs before each test in this block
    this.timeout(timeOut);
    driver.get("file://" + __dirname + "/../../site/assert.html");
  });

  // test cases

  var url = "";


	

  test.it("Take screenshot", function() {
		// this won't save to file, as Take screenshot returns a promise 
		// driver.takeScreenshot(__dirname + "/tmp/screenshot1.png");
	
		var fs = require('fs');		
		driver.takeScreenshot().then(function(data) {
			// Base64 encoded png
			fs.writeFileSync(__dirname + "/tmp/screenshot1.png", data, 'base64');		  
		});
		
		
	});
	
	Date.prototype.yyyymmdd = function() {
	  var mm = this.getMonth() + 1; // getMonth() is zero-based
	  var dd = this.getDate();

	  return [this.getFullYear(), !mm[1] && '0', mm, !dd[1] && '0', dd].join(''); // padding
	};
	
	function writeScreenshot(data) {
	  name = new Date().yyyymmdd() + ".png";
	  var screenshotPath = __dirname + "/tmp/";	
		var fs = require('fs');			
	  fs.writeFileSync(screenshotPath + name, data, 'base64');
	};
	
	test.it("Take screenshot saved to timestamped file", function() {
		driver.takeScreenshot().then(function(data) {
			writeScreenshot(data);
		});
  });


});
Practice recipe for taking a time-stamped screenshot using Selenium

Leave browser open after test finishes

Whenever an error or a failure occurs during the test execution, a ...