user-event/base tests

Author: mdjastrzebski

AGENTS.md

@@ -41,6 +41,7 @@ The project uses `yarn` for dependency management and script execution.
   - **Location:** Tests are located within `src`, typically co-located in `__tests__` directories.
   - **Setup:** `jest-setup.ts` configures the test environment. `src/index.ts` automatically configures cleanup after each test unless skipped.
   - **Coverage:** Collected from `src`, excluding tests.
+  - **Organization:** Use `describe` to group test by theme. Avoid putting all tests in the same `describe` block. Avoid `describe` nesting. Avoid `describe` with only single test, make that test top-level. Prefere `test` over `it`.
 
 - **Commits & Releases:**
   - **Commits:** Follow the **Conventional Commits** specification (e.g., `fix:`, `feat:`, `chore:`). This is enforced and used for changelog generation.

src/user-event/event-builder/__tests__/base.test.ts

@@ -0,0 +1,35 @@
+import { baseSyntheticEvent } from '../base';
+
+test('returns object with all required properties and default values', () => {
+  const event = baseSyntheticEvent();
+
+  expect(event.currentTarget).toEqual({});
+  expect(event.target).toEqual({});
+  expect(event.timeStamp).toBe(0);
+  expect(event.isDefaultPrevented?.()).toBe(false);
+  expect(event.isPropagationStopped?.()).toBe(false);
+  expect(event.isPersistent?.()).toBe(false);
+  expect(typeof event.stopPropagation).toBe('function');
+  expect(typeof event.preventDefault).toBe('function');
+  expect(typeof event.persist).toBe('function');
+});
+
+test('returns a new object instance on each call', () => {
+  const event1 = baseSyntheticEvent();
+  const event2 = baseSyntheticEvent();
+
+  expect(event1).not.toBe(event2);
+  expect(event1.currentTarget).not.toBe(event2.currentTarget);
+  expect(event1.target).not.toBe(event2.target);
+});
+
+test('can be spread into other objects', () => {
+  const extendedEvent = {
+    ...baseSyntheticEvent(),
+    nativeEvent: { test: 'value' },
+  };
+
+  expect(extendedEvent).toHaveProperty('currentTarget');
+  expect(extendedEvent).toHaveProperty('preventDefault');
+  expect(extendedEvent.nativeEvent).toEqual({ test: 'value' });
+});

src/user-event/event-builder/base.ts

@@ -1,7 +1,12 @@
 import type { BaseSyntheticEvent } from 'react';
 
 /** Builds base syntentic event stub, with prop values as inspected in RN runtime. */
-export function baseSyntheticEvent(): Partial<BaseSyntheticEvent<object, unknown, unknown>> {
+type BaseEvent = Partial<BaseSyntheticEvent<object, unknown, unknown>> & {
+  // `isPersistent` is not a standard prop, but it's used in RN runtime. See: https://react.dev/reference/react-dom/components/common#react-event-object-methods
+  isPersistent: () => boolean;
+};
+
+export function baseSyntheticEvent(): BaseEvent {
   return {
     currentTarget: {},
     target: {},
@@ -10,7 +15,6 @@ export function baseSyntheticEvent(): Partial<BaseSyntheticEvent<object, unknown
     stopPropagation: () => {},
     isPropagationStopped: () => false,
     persist: () => {},
-    // @ts-expect-error: `isPersistent` is not a standard prop, but it's used in RN runtime. See: https://react.dev/reference/react-dom/components/common#react-event-object-methods
     isPersistent: () => false,
     timeStamp: 0,
   };