add tracing client test

dart/lib/src/http_client/tracing_client.dart

@@ -59,8 +59,7 @@ class TracingClient extends BaseClient {
           final scope = _hub.scope;
           final propagationContext = scope.propagationContext;
 
-          final traceHeader = SentryTraceHeader(
-              propagationContext.traceId, propagationContext.spanId);
+          final traceHeader = propagationContext.toSentryTrace();
           addSentryTraceheader(traceHeader, request.headers);
 
           final baggage = propagationContext.baggage;

dart/lib/src/hub_adapter.dart

@@ -5,6 +5,7 @@ import 'hint.dart';
 
 import 'hub.dart';
 import 'protocol.dart';
+import 'scope.dart';
 import 'sentry.dart';
 import 'sentry_client.dart';
 import 'sentry_user_feedback.dart';
@@ -166,4 +167,7 @@ class HubAdapter implements Hub {
     String transaction,
   ) =>
       Sentry.currentHub.setSpanContext(throwable, span, transaction);
+
+  @override
+  Scope get scope => Sentry.currentHub.scope;
 }

dart/lib/src/noop_hub.dart

@@ -5,6 +5,7 @@ import 'package:meta/meta.dart';
 import 'hint.dart';
 import 'hub.dart';
 import 'protocol.dart';
+import 'scope.dart';
 import 'sentry_client.dart';
 import 'sentry_options.dart';
 import 'sentry_user_feedback.dart';
@@ -118,4 +119,7 @@ class NoOpHub implements Hub {
 
   @override
   void setSpanContext(throwable, ISentrySpan span, String transaction) {}
+
+  @override
+  Scope get scope => Scope(_options);
 }

dart/lib/src/propagation_context.dart

@@ -12,4 +12,6 @@ class PropagationContext {
     traceId = SentryId.newId();
     spanId = SpanId.newId();
   }
+
+  SentryTraceHeader toSentryTrace() => SentryTraceHeader(traceId, spanId);
 }

dart/test/http_client/tracing_client_test.dart

@@ -188,6 +188,37 @@ void main() {
 
       await sut.get(requestUri);
     });
+
+    test('set headers from propagationContext when tracing is disabled', () async {
+      fixture._options.enableTracing = false;
+      final sut = fixture.getSut(
+        client: fixture.getClient(statusCode: 200, reason: 'OK'),
+      );
+
+      final propagationContext = fixture._hub.scope.propagationContext;
+      propagationContext.baggage = SentryBaggage({'foo': 'bar'});
+
+      final response = await sut.get(requestUri);
+
+      expect(response.request!.headers['sentry-trace'],
+          propagationContext.toSentryTrace().value);
+      expect(response.request!.headers['baggage'], 'foo=bar');
+    });
+
+    test('set headers from propagationContext when no transaction', () async {
+      final sut = fixture.getSut(
+        client: fixture.getClient(statusCode: 200, reason: 'OK'),
+      );
+
+      final propagationContext = fixture._hub.scope.propagationContext;
+      propagationContext.baggage = SentryBaggage({'foo': 'bar'});
+
+      final response = await sut.get(requestUri);
+
+      expect(response.request!.headers['sentry-trace'],
+          propagationContext.toSentryTrace().value);
+      expect(response.request!.headers['baggage'], 'foo=bar');
+    });
   });
 }