As per your question and code block as you are using the following Test Configuration:
- Selenium => 3.14
- geckodriver => 0.21.0
- Firefox => 61.0.2
You have to use the capability marionette mandatorily. To achieve that either:
- You can leave the capability marionette untouched as by default
marionetteis set to True. -
You can also specify the capability marionette as follows:
cap = DesiredCapabilities().FIREFOX cap["marionette"] = True
This usecase
This error message…
selenium.common.exceptions.SessionNotCreatedException: Message: Unable to find a matching set of capabilities
…implies that the GeckoDriver was unable to initiate/spawn a new WebBrowser i.e. Firefox Browser session.
There are numerous possibilities behind the error you are seeing and can be solved through any of the following steps mentioned below:
-
As you are on Windows OS you need to pass the key executable_path along with the value containing:
- Absolute path of the GeckoDriver.
- The Absolute path of the GeckoDriver should be mentioned through single quotes and single backward slash along with the raw (
r) switch. - Include the extension of the GeckoDriver binary.
-
Your line of code will be:
driver = Firefox(executable_path=r'C:\path\to\geckodriver.exe', firefox_options=options, capabilities=cap)
References
- selenium.common.exceptions.SessionNotCreatedException: Message: Unable to find a matching set of capabilities with Firefox 46 through Selenium
- How can Geckodriver/Firefox work without Marionette? (running python selenium 3 against FF 53)