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Troubleshooting Assistance

How to get manage WebDriver problems.

It is not always obvious the root cause of errors in Selenium.

  1. The most common Selenium-related error is a result of poor synchronization. Read about Waiting Strategies. If you aren’t sure if it is a synchronization strategy you can try temporarily hard coding a large sleep where you see the issue, and you’ll know if adding an explicit wait can help.

  2. Note that many errors that get reported to the project are actually caused by issues in the underlying drivers that Selenium sends the commands to. You can rule out a driver problem by executing the command in multiple browsers.

  3. If you have questions about how to do things, check out the Support options for ways get assistance.

  4. If you think you’ve found a problem with Selenium code, go ahead and file a Bug Report on GitHub.

1 - Understanding Common Errors

How to get deal with various problems in your Selenium code.

Invalid Selector Exception

CSS and XPath Selectors are sometimes difficult to get correct.

Likely Cause

The CSS or XPath selector you are trying to use has invalid characters or an invalid query.

Possible Solutions

Run your selector through a validator service:

Or use a browser extension to get a known good value:

No Such Element Exception

The element can not be found at the exact moment you attempted to locate it.

Likely Cause

  • You are looking for the element in the wrong place (perhaps a previous action was unsuccessful).
  • You are looking for the element at the wrong time (the element has not shown up in the DOM, yet)
  • The locator has changed since you wrote the code

Possible Solutions

  • Make sure you are on the page you expect to be on, and that previous actions in your code completed correctly
  • Make sure you are using a proper Waiting Strategy
  • Update the locator with the browser’s devtools console or use a browser extension like:

Stale Element Reference Exception

An element goes stale when it was previously located, but can not be currently accessed. Elements do not get relocated automatically; the driver creates a reference ID for the element and has a particular place it expects to find it in the DOM. If it can not find the element in the current DOM, any action using that element will result in this exception.

Common Causes

This can happen when:

  • You have refreshed the page, or the DOM of the page has dynamically changed.
  • You have navigated to a different page.
  • You have switched to another window or into or out of a frame or iframe.

Common Solutions

The DOM has changed

When the page is refreshed or items on the page have moved around, there is still an element with the desired locator on the page, it is just no longer accessible by the element object being used, and the element must be relocated before it can be used again. This is often done in one of two ways:

  • Always relocate the element every time you go to use it. The likelihood of the element going stale in the microseconds between locating and using the element is small, though possible. The downside is that this is not the most efficient approach, especially when running on a remote grid.

  • Wrap the Web Element with another object that stores the locator, and caches the located Selenium element. When taking actions with this wrapped object, you can attempt to use the cached object if previously located, and if it is stale, exception can be caught, the element relocated with the stored locator, and the method re-tried. This is more efficient, but it can cause problems if the locator you’re using references a different element (and not the one you want) after the page has changed.

The Context has changed

Element objects are stored for a given context, so if you move to a different context — like a different window or a different frame or iframe — the element reference will still be valid, but will be temporarily inaccessible. In this scenario, it won’t help to relocate the element, because it doesn’t exist in the current context. To fix this, you need to make sure to switch back to the correct context before using the element.

The Page has changed

This scenario is when you haven’t just changed contexts, you have navigated to another page and have destroyed the context in which the element was located. You can’t just relocate it from the current context, and you can’t switch back to an active context where it is valid. If this is the reason for your error, you must both navigate back to the correct location and relocate it.

1.1 - Unable to Locate Driver Error

Troubleshooting missing path to driver executable.

Historically, this is the most common error beginning Selenium users get when trying to run code for the first time:

The path to the driver executable must be set by the webdriver.chrome.driver system property; for more information, see https://chromedriver.chromium.org/. The latest version can be downloaded from https://chromedriver.chromium.org/downloads
The executable chromedriver needs to be available in the path.
The file geckodriver does not exist. The driver can be downloaded at https://github.com/mozilla/geckodriver/releases"
Unable to locate the chromedriver executable;

Likely cause

Through WebDriver, Selenium supports all major browsers. In order to drive the requested browser, Selenium needs to send commands to it via an executable driver. This error means the necessary driver could not be found by any of the means Selenium attempts to use.

Possible solutions

There are several ways to ensure Selenium gets the driver it needs.

Use the latest version of Selenium

As of Selenium 4.6, Selenium downloads the correct driver for you. You shouldn’t need to do anything. If you are using the latest version of Selenium and you are getting an error, please turn on logging and file a bug report with that information.

If you want to read more information about how Selenium manages driver downloads for you, you can read about the Selenium Manager.

Use the PATH environment variable

This option first requires manually downloading the driver.

This is a flexible option to change location of drivers without having to update your code, and will work on multiple machines without requiring that each machine put the drivers in the same place.

You can either place the drivers in a directory that is already listed in PATH, or you can place them in a directory and add it to PATH.

To see what directories are already on PATH, open a Terminal and execute:

echo $PATH

If the location to your driver is not already in a directory listed, you can add a new directory to PATH:

echo 'export PATH=$PATH:/path/to/driver' >> ~/.bash_profile
source ~/.bash_profile

You can test if it has been added correctly by checking the version of the driver:

chromedriver --version

To see what directories are already on PATH, open a Terminal and execute:

echo $PATH

If the location to your driver is not already in a directory listed, you can add a new directory to PATH:

echo 'export PATH=$PATH:/path/to/driver' >> ~/.zshenv
source ~/.zshenv

You can test if it has been added correctly by checking the version of the driver:

chromedriver --version

To see what directories are already on PATH, open a Command Prompt and execute:

echo %PATH%

If the location to your driver is not already in a directory listed, you can add a new directory to PATH:

setx PATH "%PATH%;C:\WebDriver\bin"

You can test if it has been added correctly by checking the version of the driver:

chromedriver.exe --version

Specify the location of the driver

If you cannot upgrade to the latest version of Selenium, you do not want Selenium to download drivers for you, and you can’t figure out the environment variables, you can specify the location of the driver in the Service object.

You first need to download the desired driver, then create an instance of the applicable Service class and set the path.

Specifying the location in the code itself has the advantage of not needing to figure out Environment Variables on your system, but has the drawback of making the code less flexible.

Driver management libraries

Before Selenium managed drivers itself, other projects were created to do so for you.

If you can’t use Selenium Manager because you are using an older version of Selenium (please upgrade), or need an advanced feature not yet implemented by Selenium Manager, you might try one of these tools to keep your drivers automatically updated:

Download the driver

Browser Supported OS Maintained by Download Issue Tracker
Chromium/Chrome Windows/macOS/Linux Google Downloads Issues
Firefox Windows/macOS/Linux Mozilla Downloads Issues
Edge Windows/macOS/Linux Microsoft Downloads Issues
Internet Explorer Windows Selenium Project Downloads Issues
Safari macOS High Sierra and newer Apple Built in Issues

Note: The Opera driver no longer works with the latest functionality of Selenium and is currently officially unsupported.

2 - Logging Selenium commands

Getting information about Selenium execution.

Turning on logging is a valuable way to get extra information that might help you determine why you might be having a problem.

Getting a logger

Java logs are typically created per class. You can work with the default logger to work with all loggers. To filter out specific classes, see Filtering

Get the root logger:

    Logger.getLogger(SeleniumManager.class.getName()).setLevel(Level.SEVERE);
View full example on GitHub

Java Logging is not exactly straightforward, and if you are just looking for an easy way to look at the important Selenium logs, take a look at the Selenium Logger project

Python logs are typically created per module. You can match all submodules by referencing the top level module. So to work with all loggers in selenium module, you can do this:

import pytest
View full example on GitHub 
.NET does not currently have a Logging implementation

If you want to see as much debugging as possible in all the classes, you can turn on debugging globally in Ruby by setting $DEBUG = true.

For more fine-tuned control, Ruby Selenium created its own Logger class to wrap the default Logger class. This implementation provides some interesting additional features. Obtain the logger directly from the #loggerclass method on the Selenium::WebDriver module:

Selenium v4.10

      logger = Selenium::WebDriver.logger
View full example on GitHub 
const logging = require('selenium-webdriver/lib/logging')
logger = logging.getLogger('webdriver')

Logger level

Logger level helps to filter out logs based on their severity.

Java has 7 logger levels: SEVERE, WARNING, INFO, CONFIG, FINE, FINER, and FINEST. The default is INFO.

You have to change both the level of the logger and the level of the handlers on the root logger:


    Logger localLogger = Logger.getLogger(this.getClass().getName());
    localLogger.warning("this is a warning");
    localLogger.info("this is useful information");
View full example on GitHub

Python has 6 logger levels: CRITICAL, ERROR, WARNING, INFO, DEBUG, and NOTSET. The default is WARNING

To change the level of the logger:

View full example on GitHub

Things get complicated when you use PyTest, though. By default, PyTest hides logging unless the test fails. You need to set 3 things to get PyTest to display logs on passing tests.

To always output logs with PyTest you need to run with additional arguments. First, -s to prevent PyTest from capturing the console. Second, -p no:logging, which allows you to override the default PyTest logging settings so logs can be displayed regardless of errors.

So you need to set these flags in your IDE, or run PyTest on command line like:

pytest -s -p no:logging

Finally, since you turned off logging in the arguments above, you now need to add configuration to turn it back on:

logging.basicConfig(level=logging.WARN)

.NET does not currently have a Logging implementation

Ruby logger has 5 logger levels: :debug, :info, :warn, :error, :fatal. The default is :info.

To change the level of the logger:

Selenium v4.10

      logger.level = :debug
View full example on GitHub

JavaScript has 9 logger levels: OFF, SEVERE, WARNING, INFO, DEBUG, FINE, FINER, FINEST, ALL. The default is OFF.

To change the level of the logger:

logger.setLevel(logging.Level.INFO)

Actionable items

Things are logged as warnings if they are something the user needs to take action on. This is often used for deprecations. For various reasons, Selenium project does not follow standard Semantic Versioning practices. Our policy is to mark things as deprecated for 3 releases and then remove them, so deprecations may be logged as warnings.

Java logs actionable content at logger level WARN

Example:

May 08, 2023 9:23:38 PM dev.selenium.troubleshooting.LoggingTest logging
WARNING: this is a warning

Python logs actionable content at logger level — WARNING Details about deprecations are logged at this level.

Example:

WARNING  selenium:test_logging.py:23 this is a warning

.NET does not currently have a Logging implementation

Ruby logs actionable content at logger level — :warn. Details about deprecations are logged at this level.

For example:

2023-05-08 20:53:13 WARN Selenium [:example_id] this is a warning

Because these items can get annoying, we’ve provided an easy way to turn them off, see filtering section below.

Useful information

This is the default level where Selenium logs things that users should be aware of but do not need to take actions on. This might reference a new method or direct users to more information about something

Java logs useful information at logger level INFO

Example:

May 08, 2023 9:23:38 PM dev.selenium.troubleshooting.LoggingTest logging
INFO: this is useful information

Python logs useful information at logger level — INFO

Example:

INFO     selenium:test_logging.py:22 this is useful information

.NET does not currently have a Logging implementation

Ruby logs useful information at logger level — :info.

Example:

2023-05-08 20:53:13 INFO Selenium [:example_id] this is useful information

Logs useful information at level: INFO

Debugging Details

The debug log level is used for information that may be needed for diagnosing issues and troubleshooting problems.

Java logs most debug content at logger level FINE

Example:

May 08, 2023 9:23:38 PM dev.selenium.troubleshooting.LoggingTest logging
FINE: this is detailed debug information

Python logs debugging details at logger level — DEBUG

Example:

DEBUG    selenium:test_logging.py:24 this is detailed debug information

.NET does not currently have a Logging implementation

Ruby only provides one level for debugging, so all details are at logger level — :debug.

Example:

2023-05-08 20:53:13 DEBUG Selenium [:example_id] this is detailed debug information

Logs debugging details at level: FINER and FINEST

Logger output

Logs can be displayed in the console or stored in a file. Different languages have different defaults.

By default all logs are sent to System.err. To direct output to a file, you need to add a handler:


    byte[] bytes = Files.readAllBytes(Paths.get("selenium.xml"));
View full example on GitHub

By default all logs are sent to sys.stderr. To direct output somewhere else, you need to add a handler with either a StreamHandler or a FileHandler:

    logger = logging.getLogger('selenium')
View full example on GitHub 
.NET does not currently have a Logging implementation

By default, logs are sent to the console in stdout.
To store the logs in a file:

Selenium v4.10

      logger.output = file_name
View full example on GitHub

JavaScript does not currently support sending output to a file.

To send logs to console output:

logging.installConsoleHandler()

Logger filtering

Java logging is managed on a per class level, so instead of using the root logger (Logger.getLogger("")), set the level you want to use on a per-class basis:


    Assertions.assertTrue(fileContent.contains("this is a warning"));
View full example on GitHub
Because logging is managed by module, instead of working with just "selenium", you can specify different levels for different modules: 

    log_path = "selenium.log"
View full example on GitHub 
.NET does not currently have a Logging implementation

Ruby’s logger allows you to opt in (“allow”) or opt out (“ignore”) of log messages based on their IDs. Everything that Selenium logs includes an ID. You can also turn on or off all deprecation notices by using :deprecations.

These methods accept one or more symbols or an array of symbols:

Selenium v4.10

      logger.ignore(:jwp_caps, :logger_info)
View full example on GitHub

or

Selenium v4.10

      logger.allow(%i[selenium_manager example_id])
View full example on GitHub