Quick Deploy and Fast Deploy Support
When performing a quick deploy, the test classes in the destination org don't run because they were executed as part of a previous deployment. In order to perform a quick deploy, you need to previously validate the deployment running the test classes in order to get the validation key that will allow the second deployment to be performed without running the test classes.
Copado will always try to use the quick deploy when available. If the validation key is not available or is not valid, Copado will fall back to the regular deployment option. In order to generate a validation key, the deployment must run first as validation only deployment (CheckOnly option enabled). Once this deployment is completed successfully, you can disable the CheckOnly checkbox in the deployment step of the deployment and run the same deployment again.
The deployment will contain the validation key that will allow the deployment to run without executing the test classes again in the destination org.
Copado also supports fast deploys. A fast deploy will be performed when the option Run Specified Tests is selected in the deployment. In this case, only the Apex test classes included in the deployment will be executed in the destination org.
For more information about test level deploy options, check out the article Apex Tests Run While Deploying.