Test helpers

import {
  mountWidgetFixture,
  cycleWidgetFixture,
  triggerFixture,
} from "mountly/test";

mountly/test is a tiny test-only surface for the widget contract. It is useful when you are writing adapter tests or verifying a custom widget module without going through the full on-demand feature lifecycle.

mountWidgetFixture(widget, props?, container?)

const fixture = await mountWidgetFixture(widget, { label: "ready" });

expect(fixture.container.textContent).toContain("ready");

await fixture.unmount();
fixture.container.remove();

If no container is provided, the helper creates one and appends it to document.body.

cycleWidgetFixture(widget, props?)

const result = await cycleWidgetFixture(widget, { label: "ready" });

expect(result.firstText).toContain("ready");
expect(result.afterUnmountText).toBe("");
expect(result.secondText).toContain("ready");

This catches common contract bugs: unmount() leaving DOM behind, second mount() failing, or shadow-root content not being readable in tests.

triggerFixture(options, onTrigger)

const button = document.createElement("button");
const trigger = triggerFixture(
  { type: "click", element: button, once: true },
  () => calls++,
);

trigger.fire(new MouseEvent("click", { bubbles: true }));
trigger.cleanup();

This wraps the same setupTrigger() primitive used by Mountly features, so tests exercise real trigger behavior without a full feature module.

Scope

These helpers are intentionally small. For end-to-end lifecycle tests, use createOnDemandFeature() and Playwright. For framework adapter tests, use these helpers to keep the fixture short and focused.