In addition to running unit tests, please do the following: Go to Site administration / Plugins / Activity modules / LTI Click on "Add external tool configuration" Enter anything you want for Tool Name Enter the following for Tool Base URL: http://ltiapps.net/test/tp.php Enter the following for Consumer Key: consumerkey Enter the following for Shared Secret: secret Click Save changes Go to a course. Add a new General tool activity Enter whatever you like for Activity Name Enter the following for Launch URL: http://ltiapps.net/test/tp.php Click on Show more. Enter in a description that has multiple lines. Very important that there are multiple lines. Check "Display activity description when launched" setting. For Launch Container, select Embed without blocks. Click Save and display. Should be viewing the activity now, with a description and the LTI tool should have launched. The Request summary should read "basic-lti-launch-request message request is valid." Now go back to the course. Duplicate the General tool activity that was created earlier. View the activity. Should be viewing the activity now, with a description and the LTI tool should have launched. The Request summary should read "basic-lti-launch-request message request is valid." instead of the error "Could not validate request: OAuth signature check failed - perhaps an incorrect secret or timestamp."