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ZeroTesting

Check your Swift queries and mutators against the TypeScript ones, and test code that uses a client without a server.

Overview

The drift harness

You write the Swift queries and mutators by hand, so they can drift from the TypeScript ones the server runs. zero-swift drift record runs the TypeScript definitions on sample arguments and contexts and writes a vectors file. Drift checks the Swift definitions against those vectors:

@Test @MainActor func matchesTheTSQueriesAndMutators() throws {
  let vectors = try String(contentsOf: vectorsURL, encoding: .utf8)
  let failures = try Drift.failures(
    vectors: vectors, schema: .app, queries: Queries.all, mutators: Mutators.all)
  #expect(failures == [])
}

The test fails, listing each difference, when:

  • a name is in one registry but not the other;
  • a sample's arguments don't round-trip through the Swift argument type;
  • a query builds a different AST;
  • a mutator, run on the sample's rows, changes different rows or ends differently.

A client without a server

ManualScheduler is a clock that moves only when the test advances it. MockSocketFactory hands the client sockets that the test drives as the server:

let scheduler = ManualScheduler()
let sockets = MockSocketFactory()
let zero = try Zero(
  schema: .app, context: auth, options: ZeroOptions(cacheURL: "http://zero.test"),
  scheduler: scheduler, socketFactory: sockets)

scheduler.runDueTimers()                 // the client opens its socket
let socket = try #require(sockets.sockets.first)
socket.receive(text: #"["connected",{"wsid":"w1"}]"#)
#expect(zero.connection.state == .connected)

RecordingLogSink keeps the client's log messages for a test to check.

A server in the app

For previews, demos, and UI tests that need synced data on real time, LoopbackServer plays a server in the app's process: it sends the rows it holds, confirms every query, and syncs rows added later, as another user's change would.

let server = LoopbackServer()
server.put("message", ["id": "m1", "body": "Hi", "createdAt": 1])
let zero = try Zero(
  schema: .app, options: ZeroOptions(cacheURL: "http://loopback"),
  socketFactory: server)

ZeroTesting re-exports Zero.

Topics

Drift

  • Drift

Test doubles

  • ManualScheduler
  • MockSocketFactory
  • MockSocket
  • RecordingLogSink
  • LoopbackServer