We used to joke that engineers only tested software if they lacked confidence in their code. A confident and capable engineer wouldn’t need to write tests at all; their code would always work as expected.
Encourage ‘shifting-left’ on testing, so engineers can run tests against code in development before making a pull request or committing to a repository.
In a typical waterfall software development project testing occurs after deployment to a test environment and immediately prior to https://www.bmc.com/blogs/software-deployment-vs-release/. Maybe some testing is also done in production after deployment, but the focus is on testing in the test environment.