Testing and launching an experiment

Once you've written your code, it's a good idea to test that each variant behaves as you'd expect. If you find out your implementation had a bug after you've launched the experiment, you lose days of effort as the experiment results can no longer be trusted.

The best way to do this is adding an optional override to your release conditions. For example, you can create an override to assign a user to the test variant if their email is your own (or someone in your team). To do this:

1. Go to your experiment feature flag.

2. Ensure the feature flag is enabled by checking the "Enable feature flag" box.

3. Add a new condition set with the condition to email = your_email@domain.com. Set the rollout percentage for this set to 100%.

   • In cases where email is not available (such as when your users are logged out), you can use a parameter like utm_source and append ?utm_source=your_variant_name to your URL.

4. Set the optional override for the variant you'd like to assign these users to.

5. Click "Save".

Once you test it works, launch your experiment.

Further reading

Want to learn more about how to run successful experiments in PostHog? Try these tutorials:

• A software engineer's guide to A/B testing
• 8 annoying A/B testing mistakes every engineer should know
• When and how to run group-targeted A/B tests