diff --git a/Makefile b/Makefile
index bcf217bc65..282e3a3e32 100644
--- a/Makefile
+++ b/Makefile
@@ -23,7 +23,7 @@
 # Function to expand a wildcard pattern recursively.
 rwildcard=$(strip $(foreach d,$(wildcard $1*),$(call rwildcard,$d/,$2)$(filter $(subst *,%,$2),$d)))
 
-.PHONY: all clean test benchmarks benchmark descriptorgen
+.PHONY: all clean test benchmarks benchmark descriptorgen tests
 CC=gcc
 CXX=g++
 CFLAGS=-std=c99
@@ -34,10 +34,13 @@ LDLIBS=-lpthread
 LIBUPB=src/libupb.a
 LIBUPB_PIC=src/libupb_pic.a
 LIBUPB_SHARED=src/libupb.so
-ALL=deps $(OBJ) $(LIBUPB) $(LIBUPB_PIC)  tests/test_table tests/tests tools/upbc
+ALL=deps $(OBJ) $(LIBUPB) $(LIBUPB_PIC) tools/upbc
 all: $(ALL)
 clean:
-	rm -rf $(call rwildcard,,*.o) $(call rwildcard,,*.lo) $(ALL) benchmark/google_messages.proto.pb benchmark/google_messages.pb.* benchmarks/b.* benchmarks/*.pb*
+	rm -rf $(LIBUPB) $(LIBUPB_PIC)
+	rm -rf $(call rwildcard,,*.o) $(call rwildcard,,*.lo)
+	rm -rf benchmark/google_messages.proto.pb benchmark/google_messages.pb.* benchmarks/b.* benchmarks/*.pb*
+	rm -rf tests/tests tests/t.* tests/test_table
 	rm -rf descriptor/descriptor.proto.pb
 	cd lang_ext/python && python setup.py clean --all
 
@@ -69,8 +72,31 @@ python: $(LIBUPB_PIC)
 	cd lang_ext/python && python setup.py build
 
 # Tests
+tests: tests/tests \
+    tests/t.test_vs_proto2.googlemessage1 \
+    tests/t.test_vs_proto2.googlemessage2
+
 test: tests/tests
 	./tests/tests
+
+tests/t.test_vs_proto2.googlemessage1 \
+tests/t.test_vs_proto2.googlemessage2: \
+    tests/test_vs_proto2.cc $(LIBUPB) benchmarks/google_messages.proto.pb \
+    benchmarks/google_messages.pb.cc
+	$(CXX) $(CXXFLAGS) $(CPPFLAGS) -o tests/test_vs_proto2.googlemessage1 $< \
+	  -DMESSAGE_NAME=\"benchmarks.SpeedMessage1\" \
+	  -DMESSAGE_DESCRIPTOR_FILE=\"../benchmarks/google_messages.proto.pb\" \
+	  -DMESSAGE_FILE=\"../benchmarks/google_message1.dat\" \
+	  -DMESSAGE_CIDENT="benchmarks::SpeedMessage1" \
+	  -DMESSAGE_HFILE=\"../benchmarks/google_messages.pb.h\" \
+	  benchmarks/google_messages.pb.cc -lprotobuf -lpthread $(LIBUPB)
+	$(CXX) $(CXXFLAGS) $(CPPFLAGS) -o tests/test_vs_proto2.googlemessage2 $< \
+	  -DMESSAGE_NAME=\"benchmarks.SpeedMessage2\" \
+	  -DMESSAGE_DESCRIPTOR_FILE=\"../benchmarks/google_messages.proto.pb\" \
+	  -DMESSAGE_FILE=\"../benchmarks/google_message2.dat\" \
+	  -DMESSAGE_CIDENT="benchmarks::SpeedMessage2" \
+	  -DMESSAGE_HFILE=\"../benchmarks/google_messages.pb.h\" \
+	  benchmarks/google_messages.pb.cc -lprotobuf -lpthread $(LIBUPB)
 tests/test_table: src/libupb.a
 tests/tests: src/libupb.a
 
diff --git a/tests/test_vs_proto2.cc b/tests/test_vs_proto2.cc
new file mode 100644
index 0000000000..e284100f39
--- /dev/null
+++ b/tests/test_vs_proto2.cc
@@ -0,0 +1,220 @@
+
+#undef NDEBUG  /* ensure tests always assert. */
+#include <assert.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <google/protobuf/descriptor.h>
+#include "upb_parse.h"
+#include "upb_context.h"
+#include "upb_context.h"
+#include "upb_msg.h"
+#include "upb_mm.h"
+
+int num_assertions = 0;
+#define ASSERT(expr) do { \
+  ++num_assertions; \
+  assert(expr); \
+  } while(0)
+
+#include MESSAGE_HFILE
+
+void compare(const google::protobuf::Message& proto2_msg,
+             struct upb_msg *upb_msg);
+
+void compare_arrays(const google::protobuf::Reflection *r,
+                    const google::protobuf::Message& proto2_msg,
+                    const google::protobuf::FieldDescriptor *proto2_f,
+                    struct upb_msg *upb_msg, struct upb_msg_fielddef *upb_f)
+{
+  struct upb_array *arr = *upb_msg_getptr(upb_msg, upb_f).arr;
+  ASSERT(arr->len == (upb_arraylen_t)r->FieldSize(proto2_msg, proto2_f));
+  for(upb_arraylen_t i = 0; i < arr->len; i++) {
+    union upb_value_ptr p = upb_array_getelementptr(arr, i);
+    switch(upb_f->type) {
+      default:
+        ASSERT(false);
+      case UPB_TYPENUM(DOUBLE):
+        ASSERT(r->GetRepeatedDouble(proto2_msg, proto2_f, i) == *p._double);
+        break;
+      case UPB_TYPENUM(FLOAT):
+        ASSERT(r->GetRepeatedFloat(proto2_msg, proto2_f, i) == *p._float);
+        break;
+      case UPB_TYPENUM(INT64):
+      case UPB_TYPENUM(SINT64):
+      case UPB_TYPENUM(SFIXED64):
+        ASSERT(r->GetRepeatedInt64(proto2_msg, proto2_f, i) == *p.int64);
+        break;
+      case UPB_TYPENUM(UINT64):
+      case UPB_TYPENUM(FIXED64):
+        ASSERT(r->GetRepeatedUInt64(proto2_msg, proto2_f, i) == *p.uint64);
+        break;
+      case UPB_TYPENUM(SFIXED32):
+      case UPB_TYPENUM(SINT32):
+      case UPB_TYPENUM(INT32):
+      case UPB_TYPENUM(ENUM):
+        ASSERT(r->GetRepeatedInt32(proto2_msg, proto2_f, i) == *p.int32);
+        break;
+      case UPB_TYPENUM(FIXED32):
+      case UPB_TYPENUM(UINT32):
+        ASSERT(r->GetRepeatedUInt32(proto2_msg, proto2_f, i) == *p.uint32);
+        break;
+      case UPB_TYPENUM(BOOL):
+        ASSERT(r->GetRepeatedBool(proto2_msg, proto2_f, i) == *p._bool);
+        break;
+      case UPB_TYPENUM(STRING):
+      case UPB_TYPENUM(BYTES): {
+        std::string str = r->GetRepeatedString(proto2_msg, proto2_f, i);
+        std::string str2((*p.str)->ptr, (*p.str)->byte_len);
+        ASSERT(str == str2);
+        break;
+      }
+      case UPB_TYPENUM(GROUP):
+      case UPB_TYPENUM(MESSAGE):
+        compare(r->GetRepeatedMessage(proto2_msg, proto2_f, i), *p.msg);
+    }
+  }
+}
+
+void compare_values(const google::protobuf::Reflection *r,
+                    const google::protobuf::Message& proto2_msg,
+                    const google::protobuf::FieldDescriptor *proto2_f,
+                    struct upb_msg *upb_msg, struct upb_msg_fielddef *upb_f)
+{
+  union upb_value_ptr p = upb_msg_getptr(upb_msg, upb_f);
+  switch(upb_f->type) {
+    default:
+      ASSERT(false);
+    case UPB_TYPENUM(DOUBLE):
+      ASSERT(r->GetDouble(proto2_msg, proto2_f) == *p._double);
+      break;
+    case UPB_TYPENUM(FLOAT):
+      ASSERT(r->GetFloat(proto2_msg, proto2_f) == *p._float);
+      break;
+    case UPB_TYPENUM(INT64):
+    case UPB_TYPENUM(SINT64):
+    case UPB_TYPENUM(SFIXED64):
+      ASSERT(r->GetInt64(proto2_msg, proto2_f) == *p.int64);
+      break;
+    case UPB_TYPENUM(UINT64):
+    case UPB_TYPENUM(FIXED64):
+      ASSERT(r->GetUInt64(proto2_msg, proto2_f) == *p.uint64);
+      break;
+    case UPB_TYPENUM(SFIXED32):
+    case UPB_TYPENUM(SINT32):
+    case UPB_TYPENUM(INT32):
+    case UPB_TYPENUM(ENUM):
+      ASSERT(r->GetInt32(proto2_msg, proto2_f) == *p.int32);
+      break;
+    case UPB_TYPENUM(FIXED32):
+    case UPB_TYPENUM(UINT32):
+      ASSERT(r->GetUInt32(proto2_msg, proto2_f) == *p.uint32);
+      break;
+    case UPB_TYPENUM(BOOL):
+      ASSERT(r->GetBool(proto2_msg, proto2_f) == *p._bool);
+      break;
+    case UPB_TYPENUM(STRING):
+    case UPB_TYPENUM(BYTES): {
+      std::string str = r->GetString(proto2_msg, proto2_f);
+      std::string str2((*p.str)->ptr, (*p.str)->byte_len);
+      ASSERT(str == str2);
+      break;
+    }
+    case UPB_TYPENUM(GROUP):
+    case UPB_TYPENUM(MESSAGE):
+      compare(r->GetMessage(proto2_msg, proto2_f), *p.msg);
+  }
+}
+
+void compare(const google::protobuf::Message& proto2_msg,
+             struct upb_msg *upb_msg)
+{
+  const google::protobuf::Reflection *r = proto2_msg.GetReflection();
+  const google::protobuf::Descriptor *d = proto2_msg.GetDescriptor();
+  struct upb_msgdef *def = upb_msg->def;
+
+  ASSERT((uint32_t)d->field_count() == def->num_fields);
+  for(uint32_t i = 0; i < def->num_fields; i++) {
+    struct upb_msg_fielddef *upb_f = &def->fields[i];
+    struct google_protobuf_FieldDescriptorProto *upb_fd =
+        upb_msg_field_descriptor(upb_f, def);
+    const google::protobuf::FieldDescriptor *proto2_f =
+        d->FindFieldByNumber(upb_fd->number);
+    // Make sure the definitions are equal.
+    ASSERT(upb_f);
+    ASSERT(upb_fd);
+    ASSERT(proto2_f);
+    ASSERT(upb_fd->number == proto2_f->number());
+    ASSERT(std::string(upb_fd->name->ptr, upb_fd->name->byte_len) ==
+           proto2_f->name());
+    ASSERT(upb_fd->type == proto2_f->type());
+    ASSERT(upb_isarray(upb_f) == proto2_f->is_repeated());
+
+    if(!upb_msg_isset(upb_msg, upb_f)) {
+      if(upb_isarray(upb_f))
+        ASSERT(r->FieldSize(proto2_msg, proto2_f) == 0);
+      else
+        ASSERT(r->HasField(proto2_msg, proto2_f) == false);
+    } else {
+      if(upb_isarray(upb_f))
+        compare_arrays(r, proto2_msg, proto2_f, upb_msg, upb_f);
+      else
+        compare_values(r, proto2_msg, proto2_f, upb_msg, upb_f);
+    }
+  }
+}
+
+void parse_and_compare(MESSAGE_CIDENT *proto2_msg, struct upb_msg *upb_msg,
+                       struct upb_string *str)
+{
+  // Parse to both proto2 and upb.
+  ASSERT(proto2_msg->ParseFromArray(str->ptr, str->byte_len));
+  ASSERT(upb_msg_parsestr(upb_msg, str->ptr, str->byte_len) == UPB_STATUS_OK);
+  compare(*proto2_msg, upb_msg);
+}
+
+int main()
+{
+  // Initialize upb state, parse descriptor.
+  struct upb_context *c = upb_context_new();
+  struct upb_string *fds = upb_strreadfile(MESSAGE_DESCRIPTOR_FILE);
+  if(!fds) {
+    fprintf(stderr, "Couldn't read " MESSAGE_DESCRIPTOR_FILE ".\n");
+    return 1;
+  }
+  if(!upb_context_parsefds(c, fds)) {
+    fprintf(stderr, "Error importing " MESSAGE_DESCRIPTOR_FILE ".\n");
+    return 1;
+  }
+  upb_string_unref(fds);
+
+  struct upb_string *proto_name = upb_strdupc(MESSAGE_NAME);
+  struct upb_symtab_entry e;
+  bool success = upb_context_lookup(c, proto_name, &e);
+  if(!success || e.type != UPB_SYM_MESSAGE) {
+    fprintf(stderr, "Error finding symbol '" UPB_STRFMT "'.\n",
+            UPB_STRARG(proto_name));
+    return 1;
+  }
+  upb_string_unref(proto_name);
+  struct upb_msgdef *def = e.ref.msg;
+
+  // Read the message data itself.
+  struct upb_string *str = upb_strreadfile(MESSAGE_FILE);
+  if(!str) {
+    fprintf(stderr, "Error reading " MESSAGE_FILE "\n");
+    return 1;
+  }
+
+  // Run twice to test proper object reuse.
+  MESSAGE_CIDENT proto2_msg;
+  struct upb_msg *upb_msg = upb_msg_new(def);
+  parse_and_compare(&proto2_msg, upb_msg, str);
+  parse_and_compare(&proto2_msg, upb_msg, str);
+  printf("All tests passed, %d assertions.\n", num_assertions);
+
+  upb_msg_unref(upb_msg);
+  upb_string_unref(str);
+  upb_context_unref(c);
+
+  return 0;
+}