fixup test_core constraint
diff --git a/pkgs/test/pubspec.yaml b/pkgs/test/pubspec.yaml
index c0b5853..0a16b30 100644
--- a/pkgs/test/pubspec.yaml
+++ b/pkgs/test/pubspec.yaml
@@ -35,7 +35,7 @@
 
   # Use an exact version until the test_api and test_core package are stable.
   test_api: 0.6.1
-  test_core: 0.5.8
+  test_core: 0.5.9
 
   typed_data: ^1.3.0
   web_socket_channel: ^2.0.0