# Gateway Testing

Gateway tests run without installed MXAccess by using fake workers, fake
transports, and in-process gRPC service fakes. Live MXAccess verification belongs
in opt-in integration tests because it depends on installed COM components and
provider state.

## Fake Worker Harness

`FakeWorkerHarness` in `src/MxGateway.Tests/Gateway/Workers/Fakes/` provides an
in-process worker side for named-pipe IPC tests. It uses the same
`WorkerFrameReader`, `WorkerFrameWriter`, and `WorkerEnvelope` contract as the
gateway so tests exercise real frame validation and worker-client state changes.

Use the harness when a gateway or session test needs worker behavior without
starting `MxGateway.Worker.exe` or loading MXAccess COM. The harness scripts:

- `WorkerHello` and `WorkerReady` startup,
- command replies with matching correlation ids,
- ordered `WorkerEvent` frames,
- `WorkerFault` frames,
- shutdown acknowledgements,
- malformed protobuf payloads and oversized frame headers,
- slow or hung workers by withholding a reply.

Session-level tests can connect the harness to the pipe created by
`SessionWorkerClientFactory` with `ConnectToGatewayPipeAsync`. Lower-level
`WorkerClient` tests can use `CreateConnectedPairAsync` to create both pipe ends
inside the test.

## Focused Commands

Run the fake worker tests after changing gateway worker IPC, session startup, or
event streaming behavior:

```bash
dotnet test src/MxGateway.Tests/MxGateway.Tests.csproj --filter FullyQualifiedName~FakeWorkerHarnessTests
dotnet test src/MxGateway.Tests/MxGateway.Tests.csproj --filter FullyQualifiedName~SessionWorkerClientFactoryFakeWorkerTests
```

Run the gateway test project after shared gateway test infrastructure changes:

```bash
dotnet test src/MxGateway.Tests/MxGateway.Tests.csproj
```

## Related Documentation

- [Gateway Process Design](./gateway-process-design.md)
- [Worker Frame Protocol](./WorkerFrameProtocol.md)
- [MXAccess Worker Instance Detailed Design](./mxaccess-worker-instance-design.md)