Have you just updated your shiny Firefox to version 3.6 and now you can’t make Selenium 1.0.1 (precisely: selenium-rc-0.1.1) working fine for you on this browser? Ooops… I got the same.

Now, when you try to run one of your Selenium based UI tests on such a brand-new-and-up-to-date “combo” it just fails to start the browser and there is just some annoying exceptions in logs, similar to these:

ERROR - Failed to start new browser session, shutdown browser and clear all session data java.lang.RuntimeException: Firefox refused shutdown while preparing a profile

org.openqa.selenium.server.browserlaunchers.FirefoxChromeLauncher$
FileLockRemainedException: Lock file still present! C:\DOCUME~1\{windows-username}\LOCALS~1\Temp\customProfileDir197b3da3c02244fb8407912c5e126b07\parent.lock

Caused by: com.thoughtworks.selenium.SeleniumException: Failed to start new browser session: Unable to delete file C:\DOCUME~1\{windows-username}\LOCALS~1\Temp\customProfileDir197b3da3c02244fb8407912c5e126b07\parent.lock

There is a cure. A bit hacky, but still worth to try, if you really need to use Firefox 3.6.

So do some search through your project dependencies JARs and find selenium-server.jar item. Unzip it, find all (of 5) “install.rdf” files inside this JAR (they are under customProfileDirCUSTFF and customProfileDirCUSTFFCHROME subfolders), open them in some text editing tool (they are XML based configuration files) and replace the max version of agent (browser) application from line like this:

<em:maxVersion>3.5.*</em:maxVersion>

into this:

<em:maxVersion>3.6.*</em:maxVersion>

Or just download customized selenium-server.jar (pathed, as above, to Firefox 3.6.*) fromthis place.

Note: If you are using Grails with Selenium plugin (selenium-rc-0.1.1), you can find selenium-server.jar in your project plugins folder (e.g. {user-home}\.grails\{grails-version}\projects\{project-name}\plugins\selenium-rc-0.1.1\lib\server)

Where:
{user-home}stands for user home folder, e.g. C:\DOCUME~1\johndoe or C:\Users\johndoe
{grails-version}is Grails version, e.g. 1.1
{project-name}is your Grails project name, e.g. test-project

Done. It should work now!