Clear error/warn message.

diff --git a/tests/tester.cc b/tests/tester.cc
index 947d02b..0d69a83 100644
--- a/tests/tester.cc
+++ b/tests/tester.cc

@@ -501,6 +501,9 @@
   }
   REQUIRE(true == ret);
 
+  err.clear();
+  warn.clear();
+
   tinygltf::Model model_empty_buffer;
   model_empty_buffer.buffers.push_back(tinygltf::Buffer());
   stream = std::stringstream();
@@ -514,6 +517,9 @@
   }
   REQUIRE(false == ret);
 
+  err.clear();
+  warn.clear();
+
   tinygltf::Model model_single_byte_buffer;
   tinygltf::Buffer buffer;
   buffer.data.push_back(0);
@@ -522,10 +528,15 @@
   ret = ctx.WriteGltfSceneToStream(&model_single_byte_buffer, stream, false, true);
   REQUIRE(ret == true);
   str = stream.str();
+  {
+    std::ofstream ofs("tmp.glb");
+    ofs.write(str.data(), str.size());
+  }
+
   bytes = (unsigned char*)str.data();
   ret = ctx.LoadBinaryFromMemory(&model_single_byte_buffer, &err, &warn, bytes, str.size());
   if (!err.empty()) {
     std::cerr << err << std::endl;
   }
   REQUIRE(true == ret);
-}
\ No newline at end of file
+}