It is not always obvious the root cause of errors in Selenium.
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.
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.
If you have questions about how to do things, check out the Support options
for ways get assistance.
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.
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.
Invalid SessionId Exception
Sometimes the session you’re trying to access is different than what’s currently available
Likely Cause
This usually occurs when the session has been deleted (e.g. driver.quit()) or if the session has changed, like when the last tab/browser has closed (e.g. driver.close())
Possible Solutions
Check your script for instances of driver.close() and driver.quit(), and any other possible causes of closed tabs/browsers. It could be that you are locating an element before you should/can.
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.
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:
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.
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:
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
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:
.NET logger is managed with a static class, so all access to logging is managed simply by referencing Log from the OpenQA.Selenium.Internal.Logging namespace.
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:
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 has 6 logger levels: Error, Warn, Info, Debug, Trace and None. The default level is Info.
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 logs actionable content at logger level Warn.
Example:
11:04:40.986 WARN LoggingTest: this is a warning
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.
Content Help
Note: This section needs additional and/or updated content
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 logs useful information at logger level Info.
Example:
11:04:40.986 INFO LoggingTest: this is useful information
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
Content Help
Note: This section needs additional and/or updated content
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:
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:
<dependencies><!-- more dependencies ... --><dependency><groupId>org.seleniumhq.selenium</groupId><artifactId>selenium-java</artifactId><version>3.141.59</version></dependency><!-- more dependencies ... --></dependencies>
After
<dependencies><!-- more dependencies ... --><dependency><groupId>org.seleniumhq.selenium</groupId><artifactId>selenium-java</artifactId><version>4.4.0</version></dependency><!-- more dependencies ... --></dependencies>
var browserOptions = new ChromeOptions();
browserOptions.PlatformName = "Windows 10";
browserOptions.BrowserVersion = "latest";
var cloudOptions = new Dictionary<string, object>();
browserOptions.AddAdditionalCapability("cloud:options", cloudOptions, true);
After
var browserOptions = new ChromeOptions();
browserOptions.PlatformName = "Windows 10";
browserOptions.BrowserVersion = "latest";
var cloudOptions = new Dictionary<string, object>();
browserOptions.AddAdditionalOption("cloud:options", cloudOptions);
