Add test for non-Android platforms

Author: nohli

CHANGELOG.md

@@ -1,6 +1,7 @@
 ## 0.5.1
 
 * Add integration tests to verify plugin functionality across Android API levels
+* Add unit coverage to ensure the plugin returns `null` on non-Android platforms
 * Expand README with comprehensive troubleshooting guidance and defensive error-handling examples
 
 ## 0.5.0

test/android_id_test.dart

@@ -16,11 +16,38 @@ void main() {
   });
 
   tearDown(() {
-    TestDefaultBinaryMessengerBinding.instance.defaultBinaryMessenger
-        .setMockMethodCallHandler(channel, null);
+    TestDefaultBinaryMessengerBinding.instance.defaultBinaryMessenger.setMockMethodCallHandler(channel, null);
   });
 
   test('getAndroidId', () async {
     expect(await plugin.getId(), '42');
   });
+
+  test('returns null on non-Android platforms', () async {
+    addTearDown(() => debugDefaultTargetPlatformOverride = null);
+
+    debugDefaultTargetPlatformOverride = TargetPlatform.fuchsia;
+
+    expect(await plugin.getId(), isNull);
+
+    debugDefaultTargetPlatformOverride = TargetPlatform.iOS;
+
+    expect(await plugin.getId(), isNull);
+
+    debugDefaultTargetPlatformOverride = TargetPlatform.linux;
+
+    expect(await plugin.getId(), isNull);
+
+    debugDefaultTargetPlatformOverride = TargetPlatform.macOS;
+
+    expect(await plugin.getId(), isNull);
+
+    debugDefaultTargetPlatformOverride = TargetPlatform.windows;
+
+    expect(await plugin.getId(), isNull);
+
+    debugDefaultTargetPlatformOverride = TargetPlatform.android;
+
+    expect(await plugin.getId(), '42');
+  });
 }