test: cover the switch handle growing on press

Removing the 100ms delay was a user-visible fix with no test behind it, so the
delay could have come back unnoticed.

Asserting the size needs a testID on the view that carries it: `-handle` now
names the view holding the handle's size and position, and the tinted fill
inside it becomes `-handle-fill`.

Author: likevy

src/components/Switch/Switch.tsx

@@ -469,7 +469,10 @@ const Switch: (props: OperableProps) => React.JSX.Element = ({
         ]}
       />
 
-      <Animated.View style={[styles.handle, anchorStyle, handleAnimatedStyle]}>
+      <Animated.View
+        testID={testID ? `${testID}-handle` : undefined}
+        style={[styles.handle, anchorStyle, handleAnimatedStyle]}
+      >
         {/* Disabled-only: opaque `surface` backdrop. The tinted fill above
             composites over it, reproducing the native math avoiding the PlatformColor alpha limitation. */}
         {isDisabled ? (
@@ -481,7 +484,7 @@ const Switch: (props: OperableProps) => React.JSX.Element = ({
           />
         ) : null}
         <Animated.View
-          testID={testID ? `${testID}-handle` : undefined}
+          testID={testID ? `${testID}-handle-fill` : undefined}
           style={[
             styles.handleFill,
             { opacity: handleOpacity },

src/components/__tests__/Switch.test.tsx

@@ -168,7 +168,7 @@ describe('Switch focus state', () => {
       <Switch value onValueChange={jest.fn()} testID="switch" />
     );
 
-    expect(animatedStyle('switch-handle')).toMatchObject({
+    expect(animatedStyle('switch-handle-fill')).toMatchObject({
       backgroundColor: defaultThemes.light.colors.primaryContainer,
     });
   });
@@ -241,6 +241,30 @@ describe('Switch operability', () => {
   });
 });
 
+describe('Switch press feedback', () => {
+  it('grows the handle to the pressed size and back on release', async () => {
+    await render(<Switch value onValueChange={jest.fn()} testID="switch" />);
+
+    await fireEvent(screen.getByTestId('switch'), 'pressIn');
+    await jest.runAllTimersAsync();
+
+    // MD3 grows the handle to 28dp while pressed, from a 24dp selected resting
+    // size. This has to be immediate -- a delay swallows short taps.
+    expect(animatedStyle('switch-handle')).toMatchObject({
+      width: 28,
+      height: 28,
+    });
+
+    await fireEvent(screen.getByTestId('switch'), 'pressOut');
+    await jest.runAllTimersAsync();
+
+    expect(animatedStyle('switch-handle')).toMatchObject({
+      width: 24,
+      height: 24,
+    });
+  });
+});
+
 describe('Switch interaction', () => {
   it('toggles to true when off and pressed', async () => {
     const user = userEvent.setup();