I am working in RedHat OpenStack project and I need to know good test cases for reliability, performance, and function test cases for RedHat OpenStack. I already looked at the Tempest test. but I'm asking if there's any other test I can follow?
I realize that you mention that you've already looked at Tempest, but I would strongly encourage you to take a second look. I understand that the documentation is a little underwhelming and tailoring the tempest configuration to your deployment can be a significant time investment. Beyond its documentation, it's a well-maintained OpenStack project and running sanity checks doesn't take too long to configure. The results can be truly revealing.
Create a tempest workspace and conduct sanity checks with --smoke or -s
Create a workspace with tempest init myworkspace. This will create the directory structure for you based off of what exists in /etc/tempest. If you've already configured your /etc/tempest, you're a step ahead, otherwise, you'll need to configure your myworkspace/etc/tempest.conf before running any test.
Once your workspace is configured for your deployment, execute tempest run --smoke from the workspace directory. This will execute ~100 smoke tests for basic cloud functionality and sanity testing. With my modest deployment, this doesn't take more than 3-5 minutes to get some worthwhile results.
Results from --subunit
Continuing with the myworkspace directory, running your smoketests with the --subunit flag (tempest run --smoke --subunit) produces the html-exportable subunit docs at workspace/.stestr/$iteration where $iteration is a 0-indexed iteration of tempest run you've executed.
For example, after your first iteration, run subunit2html .stestr/0 to generate a well-formatted results.html for your review.
Beyond Smoketesting
If you start here and iterate, I think it naturally progresses into running the full gamut of tests. The workflow is a bit different from the smoke testing:

Generally start with tempest cleanup --init-saved-state which will produce a pre-test state of your cloud, a veritable snapshot of the resources you do not want to cleanup in post. The state is stored at saved_state.json.
Run your tests with options tailored to your deployment, most basically tempest run.
After analyzing your results, a run of tempest cleanup will destroy resources that do not exists in the saved_state.json file.
Test cases for Redhat OpenStack?