During Chef cookbook testing with Test Kitchen only one “converge” action can update the Policyfile.lock.json at a time.
If you test multiple recipes in the same cookbook, wait for the “Updating policy lock using /usr/local/bin/chef-cli update” message before starting the next converge otherwise we get the error message:
STDOUT: Installing cookbooks from lock
STDERR: Error: Failed to install cookbooks from lockfile
Reason: (NoMethodError) undefined method `[]’ for nil:NilClass