[device_info_plus] Add regression integration tests

device_info_plus_tizen is a standalone Tizen plugin with its own public API
(DeviceInfoPluginTizen / TizenDeviceInfo) and does not pin a specific upstream
device_info_plus version. For reference, when the current plugin (1.4.0) was
implemented the contemporaneous upstream was device_info_plus v12.4.0
(v13.0.0 landed a couple of days later) — its data getter / deprecated toMap
API pattern is what the plugin mirrors.

The existing tests already assert every TizenDeviceInfo field; this adds
regression tests for the parts of the public API not yet covered:

- tizenInfo is consistent across repeated calls (cached/idempotent)
- TizenDeviceInfo.fromMap round-trips through the data map

Validated on a Tizen TV (10.0) and Raspberry Pi 4: all tests pass
(4 passed, 0 skipped, 0 failed).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: seungsoo47

packages/device_info_plus/CHANGELOG.md

@@ -1,3 +1,7 @@
+## NEXT
+
+* Add 2 integration test cases.
+
 ## 1.4.0
 
 * Add `freeDiskSize` and `totalDiskSize` using the Tizen Storage API.

packages/device_info_plus/example/integration_test/device_info_plus_test.dart

@@ -55,4 +55,27 @@ void main() {
       lessThanOrEqualTo(tizenInfo.physicalRamSize),
     );
   }, skip: !Platform.isLinux);
+
+  testWidgets('tizenInfo is consistent across repeated calls', (
+    WidgetTester tester,
+  ) async {
+    final deviceInfoPlugin = DeviceInfoPluginTizen();
+    final first = await deviceInfoPlugin.tizenInfo;
+    final second = await deviceInfoPlugin.tizenInfo;
+    expect(second.data, equals(first.data));
+    expect(second.modelName, first.modelName);
+  }, skip: !Platform.isLinux);
+
+  testWidgets('TizenDeviceInfo.fromMap round-trips through data', (
+    WidgetTester tester,
+  ) async {
+    final data = tizenInfo.data;
+    expect(data, isNotEmpty);
+
+    final rebuilt = TizenDeviceInfo.fromMap(data);
+    expect(rebuilt.modelName, tizenInfo.modelName);
+    expect(rebuilt.platformVersion, tizenInfo.platformVersion);
+    expect(rebuilt.screenWidth, tizenInfo.screenWidth);
+    expect(rebuilt.totalDiskSize, tizenInfo.totalDiskSize);
+  }, skip: !Platform.isLinux);
 }