Testing MLForm

Test the engine when you need deterministic state. Test mounted primitives when you need DOM behavior.

Transport unit test pattern:

const transport = {
  submit: vi.fn().mockResolvedValue({
    reports: [
      {
        backend: "default",
        mappedTo: "prediction",
        status: "ready",
        payload: { prediction: "approved" },
      },
    ],
  }),
};

const mounted = mountForm(container, { schema, transport });
await mounted.form.submit();

expect(transport.submit).toHaveBeenCalledWith(
  expect.objectContaining({ modelValues: expect.any(Object) }),
);

Recommended coverage:

Feature	Test
Field constraints	form.validate() returns expected field errors.
Cross-field validators	Invalid combinations block submit.
Hooks	Hooks receive values, result, and submit count.
Custom fields	Definition normalizes, serializes, validates, and describes.
Custom renderers	Primitive registry maps descriptor component to a valid custom element.