Without going too deeply into details, we use common non-cloud-native platforms such as Jenkins to configure and schedule the tests. Unit tests are often baked into Makefiles while functional / integration tests are usually written as shell scripts, python scripts, or (depending on what needs to happen) even Ansible playbooks. This allows us to avoid cloud vendor lock-in, while using the cloud to host this infra and the deployment envs themselves.

Edit: we use Makefiles, not because we are writing code in C (we are not) but because our tech culture is very familiar with using 'make' to orchestrate polyglot language builds and deployments.