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A service built on Restate tests its durable code in three layers. Each layer proves something the others cannot and needs its own setup. The two automated layers each carry a command, and the operator gate runs by hand.

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The three layers

The operator gate has no command. A person runs it before a work step closes, and it:
  • runs against a test organisation, never production
  • cleans up whatever it creates
  • records its results on the issue

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The harness shape

A single harness file declares the test server, its two variants, and the fetch helpers that call handlers over the wire. A test file imports these and never declares its own, so every scenario boots the server and reads a response the same way. The two variants boot the same services with different server options:
  • alwaysReplay forces the server to suspend and replay the handler at every step, so a handler that is not deterministic on replay fails here.
  • disableRetries fails a thrown handler error at once instead of retrying it, so an error path surfaces without waiting out a backoff.
The empty-body rule. A handler with no return value answers a success with an empty response body. The fetch helpers read the response as text and treat an empty body as no value, rather than parsing it as JSON and failing.

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Databases

Each CI run gets a fresh Neon branch, created from a clean test branch that already carries seed data.
Never create the CI branch from production. A branch copies every row, including the auth signing keys — branching production hands those keys to CI.

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Credentials in CI

CI never holds a credential that can create real infrastructure, such as a Fly organization token. Any check that needs one of those credentials belongs to the operator gate, where a person runs it — not a CI step.

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When to write which test

Ask one question of the assertion: with Restate removed, would it still mean something?
  • Yes — write a unit test — parsing, a branch, an error-to-status mapping, a wire shape.
  • No — write a Restate scenario. The assertion is about what the engine does with the handler: serialisation, retry, idempotency, suspension, replay determinism.
  • Neither can be faked — use the operator gate. The check needs a real third-party system and runs by hand.
  • A slow time boundary stays in the unit tier. Factor a real wait into a pure function and test that function, rather than making a scenario wait out the clock.