The behavior of Apex test runs in a Salesforce deployment depends on whether you are running a deployment validation or a "real" deployment.
During a deployment validation, a.k.a check-only deployment, Salto will ask you which tests you want to run as part of the validation
If your validation succeeds, including apex tests, you will be able to perform a "Quick Deploy"
For "normal" or "real" deployments, you can configure the Apex test runs following these steps
1- On a deployment, click the three-dot menu and select Configure Deployment
2- Click Configuration next to the salesforce checkbox
3- From here, you can specify the apex test behavior.