Add unit test

packages/components/src/composite/test/index.tsx

@@ -0,0 +1,123 @@
+/**
+ * External dependencies
+ */
+import { queryByAttribute, render, screen } from '@testing-library/react';
+import { click, press, waitFor } from '@ariakit/test';
+import type { ComponentProps } from 'react';
+
+/**
+ * WordPress dependencies
+ */
+import { useState } from '@wordpress/element';
+
+/**
+ * Internal dependencies
+ */
+import { Composite } from '..';
+
+// This is necessary because of how Ariakit calculates page up and
+// page down. Without this, nothing has a height, and so paging up
+// and down doesn't behave as expected in tests.
+
+let clientHeightSpy: jest.SpiedGetter<
+	typeof HTMLElement.prototype.clientHeight
+>;
+
+beforeAll( () => {
+	clientHeightSpy = jest
+		.spyOn( HTMLElement.prototype, 'clientHeight', 'get' )
+		.mockImplementation( function getClientHeight( this: HTMLElement ) {
+			if ( this.tagName === 'BODY' ) {
+				return window.outerHeight;
+			}
+			return 50;
+		} );
+} );
+
+afterAll( () => {
+	clientHeightSpy?.mockRestore();
+} );
+
+async function renderAndValidate( ...args: Parameters< typeof render > ) {
+	const view = render( ...args );
+	await waitFor( () => {
+		const activeButton = queryByAttribute(
+			'data-active-item',
+			view.baseElement,
+			'true'
+		);
+		expect( activeButton ).not.toBeNull();
+	} );
+	return view;
+}
+
+function RemoveItemTest( props: ComponentProps< typeof Composite > ) {
+	const [ showThirdItem, setShowThirdItem ] = useState( true );
+	return (
+		<>
+			<button>Focus trap before composite</button>
+			<Composite { ...props }>
+				<Composite.Item>Item 1</Composite.Item>
+				<Composite.Item>Item 2</Composite.Item>
+				{ showThirdItem && <Composite.Item>Item 3</Composite.Item> }
+			</Composite>
+			<button onClick={ () => setShowThirdItem( ( value ) => ! value ) }>
+				Toggle third item
+			</button>
+		</>
+	);
+}
+
+describe( 'Composite', () => {
+	it( 'should remain focussable even when there is no elements in the DOM associated with the currently active ID', async () => {
+		await renderAndValidate( <RemoveItemTest /> );
+
+		const toggleButton = screen.getByRole( 'button', {
+			name: 'Toggle third item',
+		} );
+
+		await press.Tab();
+		await press.Tab();
+
+		expect(
+			screen.getByRole( 'button', { name: 'Item 1' } )
+		).toHaveFocus();
+
+		await press.ArrowRight();
+		await press.ArrowRight();
+
+		expect(
+			screen.getByRole( 'button', { name: 'Item 3' } )
+		).toHaveFocus();
+
+		await click( toggleButton );
+
+		expect(
+			screen.queryByRole( 'button', { name: 'Item 3' } )
+		).not.toBeInTheDocument();
+
+		await press.ShiftTab();
+
+		expect(
+			screen.getByRole( 'button', { name: 'Item 2' } )
+		).toHaveFocus();
+
+		await click( toggleButton );
+
+		expect(
+			screen.getByRole( 'button', { name: 'Item 3' } )
+		).toBeVisible();
+
+		await press.ShiftTab();
+
+		expect(
+			screen.getByRole( 'button', { name: 'Item 2' } )
+		).toHaveFocus();
+
+		await press.ArrowRight();
+
+		expect(
+			screen.getByRole( 'button', { name: 'Item 3' } )
+		).toHaveFocus();
+	} );
+} );