Setup - Generate sessions (option 1 : slowest, via admin)

    Log in as admin in admin
    Click on "Selenium tests" in top menu
    Click "Generate sessions" in left menu
    Click "Generate sessions now" button
    Repeat step #4 until you get a message that number of sessions is above 450 000

Setup - Generate sessions (option 1 : faster, via db dump)

    On command line, run the following command (substitute "ezp42" with your db settings):
    mysql -u ezp42 -p ezp42 < extension/selenium/data/generic/tc-77_ezp42_450000_in_ezsession.sql

Clear the sessions

    Log in as admin in admin
    Click "Setup" in top menu
    Click "Sessions" in left menu
    Click "Remove timed out / old sessions" button
    Without waiting for step #4 to complete, Open admin in a new tab in the brower
    Verify that you don't have a deadlock by clicking these links in the admin:
    "Content structure" in top menu
    "Media library" in top menu
    "User accounts" in top menu
    Go back to the browser tab where step #4 is executing
    Wait for browser to reload.
    Verify that you don't get crash because of a timeout error. Instead, verify that eZ Publish represents to you a warning like "Not all timed out sessions where successfully removed"