add http_get_cache

experimental/http_get_cache/test/vary_header_test.dart

@@ -0,0 +1,77 @@
+import 'dart:io';
+
+import 'package:drift/native.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:http/http.dart';
+import 'package:http/testing.dart';
+import 'package:http_get_cache/http_get_cache.dart';
+
+void main() {
+  late Directory tempDir;
+  late HttpGetCacheDatabase db;
+  late SqliteHttpCacheStore store;
+
+  setUp(() {
+    tempDir = Directory.systemTemp.createTempSync('http_get_cache_test_');
+    final settings = DatabaseSettings(
+      'test.db',
+      databaseDir: tempDir.path,
+      cacheDir: tempDir.path,
+    );
+    db = HttpGetCacheDatabase(settings, NativeDatabase.memory());
+    store = SqliteHttpCacheStore(db);
+  });
+
+  tearDown(() {
+    db.close();
+    if (tempDir.existsSync()) {
+      tempDir.deleteSync(recursive: true);
+    }
+  });
+
+  test('Vary header differentiates cache entries', () async {
+    final client = MockClient((request) async {
+      return Response(
+        'Response for ${request.headers['User-Agent']}',
+        200,
+        headers: {
+          'cache-control': 'max-age=100',
+          'vary': 'User-Agent',
+        },
+      );
+    });
+
+    final cache = HttpGetCache(client, store);
+
+    // Request 1: User-Agent A
+    final req1 = Request('GET', Uri.parse('https://example.com/api'));
+    req1.headers['User-Agent'] = 'AgentA';
+    final res1 = await cache.save(req1);
+    expect(await res1.stream.bytesToString(), 'Response for AgentA');
+
+    // Request 2: User-Agent B
+    final req2 = Request('GET', Uri.parse('https://example.com/api'));
+    req2.headers['User-Agent'] = 'AgentB';
+    final res2 = await cache.save(req2);
+    expect(await res2.stream.bytesToString(), 'Response for AgentB');
+
+    // Verify correct cache hits
+
+    // Using a fail-client to ensure we hit the cache
+    final clientFail =
+        MockClient((req) async => throw Exception('Network call made!'));
+    final cacheHit = HttpGetCache(clientFail, store);
+
+    // Request 3: User-Agent A again -> Should get Cached A
+    final req3 = Request('GET', Uri.parse('https://example.com/api'));
+    req3.headers['User-Agent'] = 'AgentA';
+    final res3 = await (cacheHit.send(req3));
+    expect(await res3.stream.bytesToString(), 'Response for AgentA');
+
+    // Request 4: User-Agent B again -> Should get Cached B
+    final req4 = Request('GET', Uri.parse('https://example.com/api'));
+    req4.headers['User-Agent'] = 'AgentB';
+    final res4 = await (cacheHit.send(req4));
+    expect(await res4.stream.bytesToString(), 'Response for AgentB');
+  });
+}