diff --git a/dart/test/mocks/mock_transport.dart b/dart/test/mocks/mock_transport.dart
index ff1a611c72..fa6e033935 100644
--- a/dart/test/mocks/mock_transport.dart
+++ b/dart/test/mocks/mock_transport.dart
@@ -30,7 +30,7 @@ class MockTransport implements Transport {
       final event = await _eventFromEnvelope(envelope);
       events.add(event);
     } catch (e, stack) {
-      _exceptions += "$e\n$stack\n\n";
+      _exceptions += '$e\n$stack\n\n';
       rethrow;
     }
 
diff --git a/dio/test/mocks/mock_transport.dart b/dio/test/mocks/mock_transport.dart
index 5b9b13de03..fa6e033935 100644
--- a/dio/test/mocks/mock_transport.dart
+++ b/dio/test/mocks/mock_transport.dart
@@ -1,12 +1,19 @@
 import 'dart:convert';
 
 import 'package:sentry/sentry.dart';
-import 'no_such_method_provider.dart';
+import 'package:test/expect.dart';
 
-class MockTransport with NoSuchMethodProvider implements Transport {
+class MockTransport implements Transport {
   List<SentryEnvelope> envelopes = [];
   List<SentryEvent> events = [];
-  int calls = 0;
+
+  int _calls = 0;
+  String _exceptions = '';
+
+  int get calls {
+    expect(_exceptions, isEmpty);
+    return _calls;
+  }
 
   bool called(int calls) {
     return calls == calls;
@@ -14,11 +21,18 @@ class MockTransport with NoSuchMethodProvider implements Transport {
 
   @override
   Future<SentryId> send(SentryEnvelope envelope) async {
-    calls++;
-
-    envelopes.add(envelope);
-    final event = await _eventFromEnvelope(envelope);
-    events.add(event);
+    _calls++;
+
+    // Exception here would be swallowed by Sentry, making it hard to find test
+    // failure causes. Instead, we log them and check on access to [calls].
+    try {
+      envelopes.add(envelope);
+      final event = await _eventFromEnvelope(envelope);
+      events.add(event);
+    } catch (e, stack) {
+      _exceptions += '$e\n$stack\n\n';
+      rethrow;
+    }
 
     return envelope.header.eventId ?? SentryId.empty();
   }
@@ -28,36 +42,14 @@ class MockTransport with NoSuchMethodProvider implements Transport {
     envelopeItemData.addAll(await envelope.items.first.envelopeItemStream());
 
     final envelopeItem = utf8.decode(envelopeItemData);
-    final dynamic envelopeItemJson = jsonDecode(envelopeItem.split('\n').last);
-    final envelopeMap = envelopeItemJson as Map<String, dynamic>;
-    final requestJson = envelopeMap['request'] as Map<String, dynamic>?;
-
-    // '_InternalLinkedHashMap<dynamic, dynamic>' is not a subtype of type 'Map<String, String>'
-    final headersMap = requestJson?['headers'] as Map<String, dynamic>?;
-    final newHeadersMap = <String, String>{};
-    if (headersMap != null) {
-      for (final entry in headersMap.entries) {
-        newHeadersMap[entry.key] = entry.value as String;
-      }
-      envelopeMap['request']['headers'] = newHeadersMap;
-    }
-
-    final otherMap = requestJson?['other'] as Map<String, dynamic>?;
-    final newOtherMap = <String, String>{};
-    if (otherMap != null) {
-      for (final entry in otherMap.entries) {
-        newOtherMap[entry.key] = entry.value as String;
-      }
-      envelopeMap['request']['other'] = newOtherMap;
-    }
-
-    return SentryEvent.fromJson(envelopeMap);
+    final envelopeItemJson = jsonDecode(envelopeItem.split('\n').last);
+    return SentryEvent.fromJson(envelopeItemJson);
   }
 
   void reset() {
     envelopes.clear();
     events.clear();
-    calls = 0;
+    _calls = 0;
   }
 }