Fix null check crash in TabBar

test/providers/helpers/raw_session_retransmit_test.dart

@@ -0,0 +1,145 @@
+import 'dart:typed_data';
+
+import 'package:flutter_test/flutter_test.dart';
+import 'package:meshcore_sar_app/models/contact.dart';
+import 'package:meshcore_sar_app/providers/helpers/raw_session_retransmit.dart';
+
+class _Fragment {
+  final int index;
+  final Uint8List payload;
+
+  _Fragment(this.index, this.payload);
+}
+
+Contact _buildContact({required int outPathLen}) {
+  return Contact(
+    publicKey: Uint8List.fromList(List<int>.generate(32, (i) => i)),
+    type: ContactType.chat,
+    flags: 0,
+    outPathLen: outPathLen,
+    outPath: Uint8List.fromList(List<int>.generate(8, (i) => i + 1)),
+    advName: 'Requester',
+    lastAdvert: DateTime.now().millisecondsSinceEpoch ~/ 1000,
+    advLat: 0,
+    advLon: 0,
+    lastMod: DateTime.now().millisecondsSinceEpoch ~/ 1000,
+  );
+}
+
+void main() {
+  TestWidgetsFlutterBinding.ensureInitialized();
+
+  group('serveCachedSessionFragments', () {
+    test('returns false when sender callback is missing', () async {
+      final ok = await serveCachedSessionFragments<_Fragment>(
+        providerLabel: 'TestProvider',
+        sessionId: 'deadbeef',
+        requester: _buildContact(outPathLen: 1),
+        fragments: [
+          _Fragment(0, Uint8List.fromList([1])),
+        ],
+        maxDirectPayloadHops: 3,
+        indexOf: (f) => f.index,
+        encodeBinary: (f) => f.payload,
+        sendRawPacket: null,
+      );
+
+      expect(ok, isFalse);
+    });
+
+    test('sends only requested indices and waits for ack', () async {
+      final sent = <Uint8List>[];
+      final waited = <int>[];
+      final ok = await serveCachedSessionFragments<_Fragment>(
+        providerLabel: 'TestProvider',
+        sessionId: 'deadbeef',
+        requester: _buildContact(outPathLen: 1),
+        fragments: [
+          _Fragment(0, Uint8List.fromList([10])),
+          _Fragment(1, Uint8List.fromList([20])),
+          _Fragment(2, Uint8List.fromList([30])),
+        ],
+        maxDirectPayloadHops: 3,
+        indexOf: (f) => f.index,
+        encodeBinary: (f) => f.payload,
+        sendRawPacket:
+            ({
+              required contactPath,
+              required contactPathLen,
+              required payload,
+            }) async {
+              sent.add(payload);
+            },
+        waitForFragmentAck:
+            ({
+              required sessionId,
+              required index,
+              timeout = const Duration(seconds: 8),
+            }) async {
+              waited.add(index);
+              return true;
+            },
+        requestedIndices: {1, 2},
+      );
+
+      expect(ok, isTrue);
+      expect(sent.length, equals(2));
+      expect(sent[0], equals(Uint8List.fromList([20])));
+      expect(sent[1], equals(Uint8List.fromList([30])));
+      expect(waited, equals([1, 2]));
+    });
+
+    test('fails when ack does not arrive', () async {
+      final ok = await serveCachedSessionFragments<_Fragment>(
+        providerLabel: 'TestProvider',
+        sessionId: 'deadbeef',
+        requester: _buildContact(outPathLen: 1),
+        fragments: [
+          _Fragment(0, Uint8List.fromList([1])),
+        ],
+        maxDirectPayloadHops: 3,
+        indexOf: (f) => f.index,
+        encodeBinary: (f) => f.payload,
+        sendRawPacket:
+            ({
+              required contactPath,
+              required contactPathLen,
+              required payload,
+            }) async {},
+        waitForFragmentAck:
+            ({
+              required sessionId,
+              required index,
+              timeout = const Duration(seconds: 8),
+            }) async {
+              return false;
+            },
+      );
+
+      expect(ok, isFalse);
+    });
+
+    test('fails when no requested index matches cached fragments', () async {
+      final ok = await serveCachedSessionFragments<_Fragment>(
+        providerLabel: 'TestProvider',
+        sessionId: 'deadbeef',
+        requester: _buildContact(outPathLen: 1),
+        fragments: [
+          _Fragment(0, Uint8List.fromList([1])),
+        ],
+        maxDirectPayloadHops: 3,
+        indexOf: (f) => f.index,
+        encodeBinary: (f) => f.payload,
+        sendRawPacket:
+            ({
+              required contactPath,
+              required contactPathLen,
+              required payload,
+            }) async {},
+        requestedIndices: {99},
+      );
+
+      expect(ok, isFalse);
+    });
+  });
+}