Deterministic agent tests become much more valuable when they are expressed as reusable quality gates rather than one-off assertions scattered across test files.
A gate answers a narrow engineering question: Did the run validate before writing data? Did retries stay within policy? Was token usage recorded and within budget? Did every started span finish? The result should be stable, fast, and specific enough that a developer knows what to fix.
LLM judges still have a role in semantic evaluation. They should not be the only thing standing between a structural agent regression and production.
What Makes a Good Gate?
A practical quality gate has five properties:
