Which environment requires Apex tests even if NoTestRun is set?

In Salesforce and Copado environments, Apex tests are a fundamental part of ensuring the reliability and quality of code before it is deployed into Production. Even if the NoTestRun option is set, which generally allows for deployments to skip running tests, Production environments have a stringent requirement for Apex tests to be executed as part of the deployment process. This is because Production environments prioritize stability and must ensure that all code behaves as expected without introducing any bugs or issues that could disrupt users or business operations.

This mandatory requirement for Apex tests in Production upholds Salesforce's best practices and governance, safeguarding against potential failures due to unverified code changes. While Development, Testing, and Staging environments might have more flexibility regarding test execution, the integrity of the Production environment necessitates that tests are always run to confirm that everything is functioning properly before live deployment. Thus, the necessity for Apex tests, even when NoTestRun is set, clearly applies to the Production environment.