Lesson 1405 of 2116
Deterministic Replay With Tool Mocks for Agent Tests
Build a mock harness that lets you replay agent runs deterministically in CI.
Lesson map
What this lesson covers
Learning path
The main moves in order
- 1The premise
- 2mock tools
- 3deterministic test
- 4replay harness
Concept cluster
Terms to connect while reading
Section 1
The premise
Real tool calls in tests are flaky and expensive — mock harnesses keep agent tests fast and stable.
What AI does well here
- Record real tool responses for use as mocks.
- Replay against a fixed seed for stable runs.
- Allow override of specific calls for what-if analysis.
What AI cannot do
- Catch issues caused by real tool changes after recording.
- Eliminate model nondeterminism without seed control.
Key terms in this lesson
End-of-lesson quiz
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