add a failing test

packages/svelte/src/internal/client/proxy.test.ts

@@ -10,3 +10,45 @@ test('does not mutate the original object', () => {
 	assert.equal(original.x, 1);
 	assert.equal(state.x, 2);
 });
+
+test('preserves getters', () => {
+	let count = 0;
+	const original = {
+		count: 0,
+		get x() {
+			this.count += 1;
+			count += 1;
+			return 42;
+		}
+	};
+
+	const state = proxy(original);
+
+	state.x;
+	state.x;
+
+	assert.equal(original.count, 0);
+	assert.equal(count, 2);
+	assert.equal(state.count, 2);
+});
+
+test('defines a property', () => {
+	const original = {};
+	const state = proxy(original);
+
+	let value = 0;
+
+	Object.defineProperty(state, 'x', {
+		get: () => value,
+		set: (v) => (value = v)
+	});
+
+	// @ts-ignore
+	state.x = 1;
+
+	// @ts-ignore
+	assert.equal(state.x, 1);
+	assert.equal(value, 1);
+
+	assert.ok(!('x' in original));
+});