cobalt_test 0.1.2

Test helpers for Cobalt — build and tear down graphs, override dependencies, and check that a hand-written graph resolves.

cobalt_test

Test helpers for Cobalt: build and tear down graphs, override dependencies, and check that a hand-written graph resolves.

Pure Dart, on test_api and matcher rather than the full test runner, so the same helpers work under dart test and flutter test.

dev_dependencies:
  cobalt_test: ^0.1.0

Building a graph

late CobaltScope app;

setUp(() async {
  app = await cobaltTestScope(root: const AppScope(), rootName: 'app');
});

Teardown is registered for you. cobaltTestRoot() is the bare equivalent for unit tests that register a few things directly and never need two-phase startup.

Overriding

final scope = app.pushForTest()
  ..registerSingleton<Clock>(FixedClock(DateTime.utc(2026)));

Shadowing from a child is how production overrides work too, so a test uses the same mechanism the app does rather than a back door.

ownerOf<T>() answers the question that trips everyone once: a factory runs on the scope that owns its registration, not the scope you asked from, so an override below the consumer is invisible to it.

expect(scope.ownerOf<Greeter>(), same(scope)); // fails if Greeter is owned above

Checking a hand-written graph

The generator rejects an incomplete graph at build time, but it only sees what it generated. A factory never declares what it will ask for, so a graph assembled by hand can only be checked by running it:

await expectGraphResolves(app);

checkGraph returns the detail instead of throwing. Both report every hole at once — a graph with three of them should take one run to find, not three.

This is terminal for the scope. Resolving is the check, so there is no dry run, and afterwards every lazy singleton is built and owned — which changes the order teardown releases things in. Give it a scope nothing else asserts on, or make it the last thing the test does.

Two things it cannot resolve, and says so rather than passing over them:

Kind	What happens
parameterized	listed as unchecked by name, unless you pass a value in params
eager singleton	reported as resolved, but its factory ran at registration — nothing was proven

Transients are built and disposed here, since the scope does not retain them. Async singletons have their owning scope initialised first.

The rest

• DisposeRecorder — records teardown order. Its log belongs to the recorder, not to the library: teardown is not awaited, so a scope from one test can finish releasing while the next one runs, and a shared list would fail the wrong test. value and factory hand you a disposable; record is for a fixture of your own, which should capture the recorder when it is built so a late report lands in the test it came from.
• CapturingObserver — collects every event, built on Cobalt's own CobaltRecordingObserver so the wording comes from the runtime rather than a copy that drifts.
• FnFactory, ValueFactory, AsyncFnFactory, FnParamFactory — a factory from a closure, instead of declaring a class per stub, for each of the four registration shapes that take one.