Model output changes from run to run, so a test that compares an answer to one exact string will fail on correct answers. Testing agents means checking properties instead: did it call the right tool with the right arguments, does the answer contain the facts it should, does a grader model or a rule accept it. A set of such checks run over many cases is called an eval.
These guides cover the three levels most teams need. The first builds an eval suite for a whole agent, with graders and a score you can track between versions. The second brings prompts and agents into pytest so changes are checked like any other code. The third tests MCP servers directly, so a tool bug is caught before an agent ever calls it.
The code in these guides runs on Promptise Foundry, an open-source Python framework for AI agents and MCP servers.