Agents pass every test, then fail the first live webhook: why mocks lie
Common_Dream9420 · reddit · 2026-09-01
A dev recounts a recurring pitfall when building agents that handle real transactions: the agent passes every test, then fails on the first live webhook because the real provider responds differently than the mock assumed — mocks are behavioral, while the real service has memory, with auth failures, 429s and retry cycles behaving unlike guesses. They built FetchSandbox so agents run the full loop against a twin of the actual service provider, replaying recorded response patterns instead of simulations. The post ends by asking the community: are you still mocking, or testing straight against staging?
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