add a couple of unit tests

packages/svelte/src/internal/server/renderer.js

@@ -172,7 +172,7 @@ export class Renderer {
 
 	/**
 	 * @param {Record<string, any>} attrs
-	 * @param {any} body
+	 * @param {string | number | boolean | ((renderer: Renderer) => void)} body
 	 */
 	option(attrs, body) {
 		this.#out.push(`<option${attributes(attrs)}`);

packages/svelte/src/internal/server/renderer.test.ts

@@ -175,6 +175,38 @@ test('SSRState title ordering favors later lexicographic paths', () => {
 	expect(state.get_title()).toBe('E');
 });
 
+test('selects an option with an explicit value', () => {
+	const component = (renderer: Renderer) => {
+		renderer.select({ value: 2 }, (renderer) => {
+			renderer.option({ value: 1 }, (renderer) => renderer.push('one'));
+			renderer.option({ value: 2 }, (renderer) => renderer.push('two'));
+			renderer.option({ value: 3 }, (renderer) => renderer.push('three'));
+		});
+	};
+
+	const { head, body } = Renderer.render(component as unknown as Component);
+	expect(head).toBe('');
+	expect(body).toBe(
+		'<!--[--><select><option value="1">one</option><option value="2" selected>two</option><option value="3">three</option></select><!--]-->'
+	);
+});
+
+test('selects an option with an implicit value', () => {
+	const component = (renderer: Renderer) => {
+		renderer.select({ value: 'two' }, (renderer) => {
+			renderer.option({}, (renderer) => renderer.push('one'));
+			renderer.option({}, (renderer) => renderer.push('two'));
+			renderer.option({}, (renderer) => renderer.push('three'));
+		});
+	};
+
+	const { head, body } = Renderer.render(component as unknown as Component);
+	expect(head).toBe('');
+	expect(body).toBe(
+		'<!--[--><select><option>one</option><option selected>two</option><option>three</option></select><!--]-->'
+	);
+});
+
 describe('async', () => {
 	beforeAll(() => {
 		enable_async_mode_flag();