aos/flatbuffer_merge_test.cc - RealtimeRoboticsGroup/test - Gitiles

 #include "aos/flatbuffer_merge.h"

 #include <string_view>

 #include "absl/strings/escaping.h"
 #include "gtest/gtest.h"

 #include "aos/json_to_flatbuffer.h"
 #include "aos/json_to_flatbuffer_generated.h"
 #include "flatbuffers/minireflect.h"

 namespace aos {
 namespace testing {

 std::string_view FromFbb(const flatbuffers::FlatBufferBuilder &fbb) {
   return std::string_view(
       reinterpret_cast<const char *>(fbb.GetCurrentBufferPointer()),
       fbb.GetSize());
 }

 std::string_view FromFbb(const flatbuffers::DetachedBuffer &b) {
   return std::string_view(reinterpret_cast<const char *>(b.data()), b.size());
 }

 absl::Span<const uint8_t> ToSpan(const flatbuffers::DetachedBuffer &b) {
   return absl::Span<const uint8_t>(b.data(), b.size());
 }

 class FlatbufferMerge : public ::testing::Test {
  public:
   FlatbufferMerge() {}

   void ExpectMergedOutput(const flatbuffers::DetachedBuffer &fb_merged,
                           std::string_view expected_output) {
     ASSERT_NE(fb_merged.size(), 0u);

     const ::std::string merged_output =
         FlatbufferToJson(fb_merged, ConfigurationTypeTable());
     EXPECT_EQ(expected_output, merged_output);

     aos::FlatbufferDetachedBuffer<Configuration> expected_message(
         JsonToFlatbuffer(std::string(expected_output).c_str(),
                          ConfigurationTypeTable()));
     EXPECT_TRUE(
         CompareFlatBuffer(flatbuffers::GetRoot<Configuration>(fb_merged.data()),
                           &expected_message.message()));
   }

   void JsonMerge(const ::std::string in1, const ::std::string in2,
                  const ::std::string out) {
     printf("Merging: %s\n", in1.c_str());
     printf("Merging: %s\n", in2.c_str());
     const flatbuffers::DetachedBuffer fb1 = JsonToFlatbuffer(
         static_cast<const char *>(in1.c_str()), ConfigurationTypeTable());

     const ::std::string in1_nested = "{ \"nested_config\": " + in1 + " }";
     const flatbuffers::DetachedBuffer fb1_nested =
         JsonToFlatbuffer(static_cast<const char *>(in1_nested.c_str()),
                          ConfigurationTypeTable());

     const flatbuffers::DetachedBuffer fb2 = JsonToFlatbuffer(
         static_cast<const char *>(in2.c_str()), ConfigurationTypeTable());

     const ::std::string in2_nested = "{ \"nested_config\": " + in2 + " }";
     const flatbuffers::DetachedBuffer fb2_nested =
         JsonToFlatbuffer(static_cast<const char *>(in2_nested.c_str()),
                          ConfigurationTypeTable());

     const ::std::string out_nested = "{ \"nested_config\": " + out + " }";

     const flatbuffers::DetachedBuffer empty =
         JsonToFlatbuffer("{ }", ConfigurationTypeTable());

     ASSERT_NE(fb1.size(), 0u);
     ASSERT_NE(fb2.size(), 0u);
     ASSERT_NE(fb1_nested.size(), 0u);
     ASSERT_NE(fb2_nested.size(), 0u);

     // We now want to run 7 tests.
     //  in1 merged "" -> in1.
     //  in2 merged "" -> in2.
     //  "" merged in1 -> in1.
     //  "" merged in2 -> in2.
     //  nullptr merged in1 -> in1.
     //  in1 merged nullptr -> in1.
     //  in1 merged in2 -> out.

     {
       // in1 merged with "" => in1.
       flatbuffers::DetachedBuffer fb_merged =
           MergeFlatBuffers<Configuration>(fb1.data(), empty.data());
       ASSERT_NE(fb_merged.size(), 0u);

       EXPECT_EQ(in1, FlatbufferToJson(fb_merged, ConfigurationTypeTable()));
     }

     {
       // in2 merged with "" => in2.
       flatbuffers::DetachedBuffer fb_merged =
           MergeFlatBuffers<Configuration>(fb2.data(), empty.data());
       ASSERT_NE(fb_merged.size(), 0u);

       EXPECT_EQ(in2, FlatbufferToJson(fb_merged, ConfigurationTypeTable()));
     }

     {
       // "" merged with in1 => in1.
       flatbuffers::DetachedBuffer fb_merged =
           MergeFlatBuffers<Configuration>(empty.data(), fb1.data());
       ASSERT_NE(fb_merged.size(), 0u);

       EXPECT_EQ(in1, FlatbufferToJson(fb_merged, ConfigurationTypeTable()));
     }

     {
       // "" merged with in2 => in2.
       flatbuffers::DetachedBuffer fb_merged =
           MergeFlatBuffers<Configuration>(empty.data(), fb2.data());
       ASSERT_NE(fb_merged.size(), 0u);

       EXPECT_EQ(in2, FlatbufferToJson(fb_merged, ConfigurationTypeTable()));
     }

     {
       // nullptr merged with in1 => in1.
       flatbuffers::DetachedBuffer fb_merged =
           MergeFlatBuffers<Configuration>(nullptr, fb1.data());
       ASSERT_NE(fb_merged.size(), 0u);

       EXPECT_EQ(in1, FlatbufferToJson(fb_merged, ConfigurationTypeTable()));
     }

     {
       // in1 merged with nullptr => in1.
       flatbuffers::DetachedBuffer fb_merged =
           MergeFlatBuffers<Configuration>(fb1.data(), nullptr);
       ASSERT_NE(fb_merged.size(), 0u);

       EXPECT_EQ(in1, FlatbufferToJson(fb_merged, ConfigurationTypeTable()));
     }

     {
       // in1 merged with in2 => out.
       flatbuffers::DetachedBuffer fb_merged =
           MergeFlatBuffers<Configuration>(fb1.data(), fb2.data());

       ExpectMergedOutput(fb_merged, out);
     }

     // Test all the different merge methods:
     ExpectMergedOutput(
         MergeFlatBuffers(ConfigurationTypeTable(), fb1.data(), fb2.data()),
         out);
     {
       flatbuffers::FlatBufferBuilder fbb;
       fbb.ForceDefaults(true);
       fbb.Finish(MergeFlatBuffers(
           ConfigurationTypeTable(),
           flatbuffers::GetRoot<flatbuffers::Table>(fb1.data()),
           flatbuffers::GetRoot<flatbuffers::Table>(fb2.data()), &fbb));
       ExpectMergedOutput(fbb.Release(), out);
     }
     {
       flatbuffers::FlatBufferBuilder fbb;
       fbb.ForceDefaults(true);
       fbb.Finish(MergeFlatBuffers<Configuration>(
           flatbuffers::GetRoot<flatbuffers::Table>(fb1.data()),
           flatbuffers::GetRoot<flatbuffers::Table>(fb2.data()), &fbb));
       ExpectMergedOutput(fbb.Release(), out);
     }
     ExpectMergedOutput(MergeFlatBuffers<Configuration>(fb1.data(), fb2.data()),
                        out);
     ExpectMergedOutput(MergeFlatBuffers<Configuration>(fb1, fb2), out);
     ExpectMergedOutput(MergeFlatBuffers<Configuration>(
                            flatbuffers::GetRoot<Configuration>(fb1.data()),
                            flatbuffers::GetRoot<Configuration>(fb2.data()))
                            .buffer(),
                        out);

     // Now, to make things extra exciting, nest a config inside a config.  And
     // run all the tests.  This will exercise some fun nested merges and copies.

     {
       // in1_nested merged with "" => in1.
       flatbuffers::DetachedBuffer fb_merged =
           MergeFlatBuffers<Configuration>(fb1_nested.data(), empty.data());
       ASSERT_NE(fb_merged.size(), 0u);

       EXPECT_EQ(in1_nested,
                 FlatbufferToJson(fb_merged, ConfigurationTypeTable()));
     }

     {
       // in2_nested merged with "" => in2_nested.
       flatbuffers::DetachedBuffer fb_merged =
           MergeFlatBuffers<Configuration>(fb2_nested.data(), empty.data());
       ASSERT_NE(fb_merged.size(), 0u);

       EXPECT_EQ(in2_nested,
                 FlatbufferToJson(fb_merged, ConfigurationTypeTable()));
     }

     {
       // "" merged with in1_nested => in1_nested.
       flatbuffers::DetachedBuffer fb_merged =
           MergeFlatBuffers<Configuration>(empty.data(), fb1_nested.data());
       ASSERT_NE(fb_merged.size(), 0u);

       EXPECT_EQ(in1_nested,
                 FlatbufferToJson(fb_merged, ConfigurationTypeTable()));
     }

     {
       // "" merged with in2_nested => in2_nested.
       flatbuffers::DetachedBuffer fb_merged =
           MergeFlatBuffers<Configuration>(empty.data(), fb2_nested.data());
       ASSERT_NE(fb_merged.size(), 0u);

       EXPECT_EQ(in2_nested,
                 FlatbufferToJson(fb_merged, ConfigurationTypeTable()));
     }

     {
       // nullptr merged with in1_nested => in1_nested.
       flatbuffers::DetachedBuffer fb_merged =
           MergeFlatBuffers<Configuration>(nullptr, fb1_nested.data());
       ASSERT_NE(fb_merged.size(), 0u);

       EXPECT_EQ(in1_nested,
                 FlatbufferToJson(fb_merged, ConfigurationTypeTable()));
     }

     {
       // nullptr merged with in1_nested => in1_nested.
       flatbuffers::DetachedBuffer fb_merged =
           MergeFlatBuffers<Configuration>(fb1_nested.data(), nullptr);
       ASSERT_NE(fb_merged.size(), 0u);

       EXPECT_EQ(in1_nested,
                 FlatbufferToJson(fb_merged, ConfigurationTypeTable()));
     }

     {
       // in1_nested merged with in2_nested => out_nested.
       flatbuffers::DetachedBuffer fb_merged =
           MergeFlatBuffers<Configuration>(fb1_nested, fb2_nested);
       ASSERT_NE(fb_merged.size(), 0u);

       EXPECT_EQ(out_nested,
                 FlatbufferToJson(fb_merged, ConfigurationTypeTable()));
     }

     // TODO(austin): Try more flatbuffers...
     // Now try copying various flatbuffers and confirming they match.
     {
       flatbuffers::FlatBufferBuilder aos_flatbuffer_copy_fbb;
       aos_flatbuffer_copy_fbb.ForceDefaults(true);

       LOG(INFO) << "Copying " << in1 << " "
                 << absl::BytesToHexString(FromFbb(fb1)) << " at "
                 << reinterpret_cast<const void *>(fb1.data()) << " size "
                 << fb1.size();
       aos_flatbuffer_copy_fbb.Finish(CopyFlatBuffer<Configuration>(
           flatbuffers::GetRoot<Configuration>(fb1.data()),
           &aos_flatbuffer_copy_fbb));

       aos::FlatbufferDetachedBuffer<Configuration> fb_copy(
           aos_flatbuffer_copy_fbb.Release());
       ASSERT_NE(fb_copy.size(), 0u);

       flatbuffers::Verifier v(fb1.data(), fb1.size());
       EXPECT_TRUE(
           v.VerifyTable(flatbuffers::GetRoot<Configuration>(fb1.data())));

       ASSERT_TRUE(fb_copy.Verify()) << in1;

       EXPECT_EQ(in1, FlatbufferToJson(fb_copy));
     }

     {
       flatbuffers::FlatBufferBuilder aos_flatbuffer_copy_message_ptr_fbb;
       aos_flatbuffer_copy_message_ptr_fbb.ForceDefaults(true);

       aos_flatbuffer_copy_message_ptr_fbb.Finish(CopyFlatBuffer<Configuration>(
           flatbuffers::GetRoot<Configuration>(fb2.data()),
           &aos_flatbuffer_copy_message_ptr_fbb));

       aos::FlatbufferDetachedBuffer<Configuration> fb_copy_message_ptr(
           aos_flatbuffer_copy_message_ptr_fbb.Release());
       ASSERT_NE(fb_copy_message_ptr.size(), 0u);

       flatbuffers::FlatBufferBuilder aos_flatbuffer_copy_full_fbb;
       aos_flatbuffer_copy_full_fbb.ForceDefaults(true);

       aos_flatbuffer_copy_full_fbb.Finish(BlindCopyFlatBuffer<Configuration>(
           aos::FlatbufferSpan<Configuration>(ToSpan(fb2)),
           &aos_flatbuffer_copy_full_fbb));

       aos::FlatbufferDetachedBuffer<Configuration> fb_copy_full(
           aos_flatbuffer_copy_full_fbb.Release());
       ASSERT_NE(fb_copy_full.size(), 0u);

       flatbuffers::Verifier v(fb2.data(), fb2.size());
       EXPECT_TRUE(
           v.VerifyTable(flatbuffers::GetRoot<Configuration>(fb2.data())));

       LOG(INFO) << "Verifying copy of " << in2;
       ASSERT_TRUE(fb_copy_message_ptr.Verify()) << in2;
       LOG(INFO) << "Verifying full of " << in2;
       ASSERT_TRUE(fb_copy_full.Verify()) << in2;

       EXPECT_EQ(in2, FlatbufferToJson(fb_copy_message_ptr));
       EXPECT_EQ(in2, FlatbufferToJson(fb_copy_full));
     }

     {
       flatbuffers::FlatBufferBuilder aos_flatbuffer_copy_fbb;
       aos_flatbuffer_copy_fbb.ForceDefaults(true);

       aos_flatbuffer_copy_fbb.Finish(CopyFlatBuffer<Configuration>(
           flatbuffers::GetRoot<Configuration>(fb1_nested.data()),
           &aos_flatbuffer_copy_fbb));

       aos::FlatbufferDetachedBuffer<Configuration> fb_copy(
           aos_flatbuffer_copy_fbb.Release());
       ASSERT_NE(fb_copy.size(), 0u);

       ASSERT_TRUE(fb_copy.Verify());

       EXPECT_EQ(in1_nested, FlatbufferToJson(fb_copy));
     }

     {
       flatbuffers::FlatBufferBuilder aos_flatbuffer_copy_fbb;
       aos_flatbuffer_copy_fbb.ForceDefaults(true);

       aos_flatbuffer_copy_fbb.Finish(CopyFlatBuffer<Configuration>(
           flatbuffers::GetRoot<Configuration>(fb2_nested.data()),
           &aos_flatbuffer_copy_fbb));

       aos::FlatbufferDetachedBuffer<Configuration> fb_copy(
           aos_flatbuffer_copy_fbb.Release());
       ASSERT_NE(fb_copy.size(), 0u);

       ASSERT_TRUE(fb_copy.Verify());

       EXPECT_EQ(in2_nested, FlatbufferToJson(fb_copy));
     }
   }
 };

 // Test the easy ones.  Test every type, single, no nesting.
 TEST_F(FlatbufferMerge, Basic) {
   JsonMerge("{  }", "{  }", "{  }");

   JsonMerge("{ \"foo_bool\": true }", "{ \"foo_bool\": false }",
             "{ \"foo_bool\": false }");

   JsonMerge("{ \"foo_bool\": false }", "{ \"foo_bool\": true }",
             "{ \"foo_bool\": true }");

   JsonMerge("{ \"foo_byte\": 5 }", "{ \"foo_byte\": -7 }",
             "{ \"foo_byte\": -7 }");

   JsonMerge("{ \"foo_ubyte\": 5 }", "{ \"foo_ubyte\": 7 }",
             "{ \"foo_ubyte\": 7 }");

   JsonMerge("{ \"foo_short\": 5 }", "{ \"foo_short\": 7 }",
             "{ \"foo_short\": 7 }");

   JsonMerge("{ \"foo_int\": 5 }", "{ \"foo_int\": 7 }", "{ \"foo_int\": 7 }");

   JsonMerge("{ \"foo_uint\": 5 }", "{ \"foo_uint\": 7 }",
             "{ \"foo_uint\": 7 }");

   JsonMerge("{ \"foo_long\": 5 }", "{ \"foo_long\": 7 }",
             "{ \"foo_long\": 7 }");

   JsonMerge("{ \"foo_ulong\": 5 }", "{ \"foo_ulong\": 7 }",
             "{ \"foo_ulong\": 7 }");

   JsonMerge("{ \"foo_float\": 5.0 }", "{ \"foo_float\": 7.1 }",
             "{ \"foo_float\": 7.1 }");

   JsonMerge("{ \"foo_double\": 5.0 }", "{ \"foo_double\": 7.1 }",
             "{ \"foo_double\": 7.1 }");
 }

 // Test arrays of simple types.
 TEST_F(FlatbufferMerge, Array) {
   JsonMerge("{ \"foo_string\": \"baz\" }", "{ \"foo_string\": \"bar\" }",
             "{ \"foo_string\": \"bar\" }");

   JsonMerge("{ \"vector_foo_bool\": [ true, true, false ] }",
             "{ \"vector_foo_bool\": [ false, true, true, false ] }",
             "{ \"vector_foo_bool\": [ true, true, false, false, "
             "true, true, false ] }");

   JsonMerge("{ \"vector_foo_byte\": [ 9, 7, 1 ] }",
             "{ \"vector_foo_byte\": [ -3, 1, 3, 2 ] }",
             "{ \"vector_foo_byte\": [ 9, 7, 1, -3, 1, 3, 2 ] }");

   JsonMerge("{ \"vector_foo_ubyte\": [ 9, 7, 1 ] }",
             "{ \"vector_foo_ubyte\": [ 3, 1, 3, 2 ] }",
             "{ \"vector_foo_ubyte\": [ 9, 7, 1, 3, 1, 3, 2 ] }");

   JsonMerge("{ \"vector_foo_short\": [ 9, 7, 1 ] }",
             "{ \"vector_foo_short\": [ -3, 1, 3, 2 ] }",
             "{ \"vector_foo_short\": [ 9, 7, 1, -3, 1, 3, 2 ] }");

   JsonMerge("{ \"vector_foo_ushort\": [ 9, 7, 1 ] }",
             "{ \"vector_foo_ushort\": [ 3, 1, 3, 2 ] }",
             "{ \"vector_foo_ushort\": [ 9, 7, 1, 3, 1, 3, 2 ] }");

   JsonMerge("{ \"vector_foo_int\": [ 9, 7, 1 ] }",
             "{ \"vector_foo_int\": [ -3, 1, 3, 2 ] }",
             "{ \"vector_foo_int\": [ 9, 7, 1, -3, 1, 3, 2 ] }");

   JsonMerge("{ \"vector_foo_uint\": [ 9, 7, 1 ] }",
             "{ \"vector_foo_uint\": [ 3, 1, 3, 2 ] }",
             "{ \"vector_foo_uint\": [ 9, 7, 1, 3, 1, 3, 2 ] }");

   JsonMerge("{ \"vector_foo_long\": [ 9, 7, 1 ] }",
             "{ \"vector_foo_long\": [ -3, 1, 3, 2 ] }",
             "{ \"vector_foo_long\": [ 9, 7, 1, -3, 1, 3, 2 ] }");

   JsonMerge("{ \"vector_foo_ulong\": [ 9, 7, 1 ] }",
             "{ \"vector_foo_ulong\": [ 3, 1, 3, 2 ] }",
             "{ \"vector_foo_ulong\": [ 9, 7, 1, 3, 1, 3, 2 ] }");

   JsonMerge("{ \"vector_foo_float\": [ 9.0, 7.0, 1.0 ] }",
             "{ \"vector_foo_float\": [ -3.0, 1.3, 3.0, 2.0 ] }",
             "{ \"vector_foo_float\": [ 9.0, 7.0, 1.0, -3.0, 1.3, 3.0, 2.0 ] }");

   JsonMerge(
       "{ \"vector_foo_string\": [ \"9\", \"7\", \"1 \" ] }",
       "{ \"vector_foo_string\": [ \"31\", \"32\" ] }",
       "{ \"vector_foo_string\": [ \"9\", \"7\", \"1 \", \"31\", \"32\" ] }");
 }

 // Test nested messages, and arrays of nested messages.
 TEST_F(FlatbufferMerge, NestedStruct) {
   JsonMerge(
       "{ \"single_application\": { \"name\": \"woot\" } }",
       "{ \"single_application\": { \"name\": \"wow\", \"priority\": 7 } }",
       "{ \"single_application\": { \"name\": \"wow\", \"priority\": 7 } }");

   JsonMerge(
       "{ \"single_application\": { \"name\": \"wow\", \"priority\": 7 } }",
       "{ \"single_application\": { \"name\": \"woot\" } }",
       "{ \"single_application\": { \"name\": \"woot\", \"priority\": 7 } }");

   JsonMerge("{ \"apps\": [ { \"name\": \"woot\" }, { \"name\": \"wow\" } ] }",
             "{ \"apps\": [ { \"name\": \"woo2\" }, { \"name\": \"wo3\" } ] }",
             "{ \"apps\": [ { \"name\": \"woot\" }, { \"name\": \"wow\" }, { "
             "\"name\": \"woo2\" }, { \"name\": \"wo3\" } ] }");
 }

 // Test nested messages, and arrays of nested messages.
 TEST(FlatbufferCopy, WholesaleCopy) {
   flatbuffers::FlatBufferBuilder fbb_expected;
   fbb_expected.ForceDefaults(true);
   fbb_expected.DedupVtables(false);

   {
     flatbuffers::Offset<flatbuffers::String> name1_offset =
         fbb_expected.CreateString("wow");

     std::vector<flatbuffers::Offset<Application>> application_offsets;
     Application::Builder a1_builder(fbb_expected);
     a1_builder.add_name(name1_offset);
     a1_builder.add_priority(7);
     a1_builder.add_long_thingy(0x2549713132LL);
     application_offsets.emplace_back(a1_builder.Finish());

     flatbuffers::Offset<flatbuffers::String> name2_offset =
         fbb_expected.CreateString("foo");
     Application::Builder a2_builder(fbb_expected);
     a2_builder.add_name(name2_offset);
     a2_builder.add_priority(3);
     a2_builder.add_long_thingy(9);
     application_offsets.emplace_back(a2_builder.Finish());

     flatbuffers::Offset<flatbuffers::Vector<flatbuffers::Offset<Application>>>
         applications_offset = fbb_expected.CreateVector(application_offsets);

     Configuration::Builder configuration_builder(fbb_expected);
     configuration_builder.add_apps(applications_offset);
     fbb_expected.Finish(configuration_builder.Finish());
   }

   LOG(INFO) << "Initial alignment " << fbb_expected.GetBufferMinAlignment();

   aos::FlatbufferDetachedBuffer<Configuration> expected(fbb_expected.Release());

   LOG(INFO) << "Expected "
             << absl::BytesToHexString(std::string_view(
                    reinterpret_cast<char *>(expected.span().data()),
                    expected.span().size()));

   aos::FlatbufferDetachedBuffer<Application> a1 = []() {
     flatbuffers::FlatBufferBuilder fbb;
     fbb.ForceDefaults(true);

     flatbuffers::Offset<flatbuffers::String> name1_offset =
         fbb.CreateString("wow");

     Application::Builder a1_builder(fbb);
     a1_builder.add_name(name1_offset);
     a1_builder.add_priority(7);
     a1_builder.add_long_thingy(0x2549713132LL);
     flatbuffers::Offset<Application> a1 = a1_builder.Finish();

     fbb.Finish(a1);
     return fbb.Release();
   }();

   aos::FlatbufferDetachedBuffer<Application> a2 =
       JsonToFlatbuffer<Application>(static_cast<const char *>(
           "{ \"name\": \"foo\", \"priority\": 3, \"long_thingy\": 9 }"));

   aos::FlatbufferDetachedBuffer<Configuration> c1 = [&a1, &a2]() {
     flatbuffers::FlatBufferBuilder fbb;
     fbb.ForceDefaults(true);

     std::vector<flatbuffers::Offset<Application>> application_offsets;
     application_offsets.emplace_back(BlindCopyFlatBuffer(a1, &fbb));
     application_offsets.emplace_back(BlindCopyFlatBuffer(a2, &fbb));

     flatbuffers::Offset<flatbuffers::Vector<flatbuffers::Offset<Application>>>
         applications_offset = fbb.CreateVector(application_offsets);

     Configuration::Builder configuration_builder(fbb);
     configuration_builder.add_apps(applications_offset);
     fbb.Finish(configuration_builder.Finish());

     return fbb.Release();
   }();

   LOG(INFO) << "Got      "
             << absl::BytesToHexString(
                    std::string_view(reinterpret_cast<char *>(c1.span().data()),
                                     c1.span().size()));

   aos::FlatbufferDetachedBuffer<Configuration> c2 = [&a1, &a2]() {
     flatbuffers::FlatBufferBuilder fbb;
     fbb.ForceDefaults(true);

     std::vector<flatbuffers::Offset<Application>> application_offsets;
     application_offsets.emplace_back(CopyFlatBuffer(&a1.message(), &fbb));
     application_offsets.emplace_back(CopyFlatBuffer(&a2.message(), &fbb));

     flatbuffers::Offset<flatbuffers::Vector<flatbuffers::Offset<Application>>>
         applications_offset = fbb.CreateVector(application_offsets);

     Configuration::Builder configuration_builder(fbb);
     configuration_builder.add_apps(applications_offset);
     fbb.Finish(configuration_builder.Finish());

     return fbb.Release();
   }();

   LOG(INFO) << "Got      "
             << absl::BytesToHexString(
                    std::string_view(reinterpret_cast<char *>(c2.span().data()),
                                     c2.span().size()));

   ASSERT_TRUE(expected.Verify());
   ASSERT_TRUE(c1.Verify());
   ASSERT_TRUE(c2.Verify());

   LOG(INFO) << FlatbufferToJson(expected);
   LOG(INFO) << FlatbufferToJson(c1);
   LOG(INFO) << FlatbufferToJson(c2);
   EXPECT_EQ(FlatbufferToJson(expected), FlatbufferToJson(c1));
   EXPECT_EQ(FlatbufferToJson(expected), FlatbufferToJson(c2));
 }

 // Tests a compare of 2 basic (different) messages.
 TEST_F(FlatbufferMerge, CompareDifferent) {
   aos::FlatbufferDetachedBuffer<Configuration> message1(JsonToFlatbuffer(
       "{ \"single_application\": { \"name\": \"wow\", \"priority\": 7 } }",
       ConfigurationTypeTable()));
   aos::FlatbufferDetachedBuffer<Configuration> message2(JsonToFlatbuffer(
       "{ \"single_application\": { \"name\": \"wow\", \"priority\": 8 } }",
       ConfigurationTypeTable()));

   EXPECT_FALSE(CompareFlatBuffer(&message1.message(), &message2.message()));
 }

 // TODO(austin): enums
 // TODO(austin): unions
 // TODO(austin): struct

 }  // namespace testing
 }  // namespace aos
	#include "aos/flatbuffer_merge.h"

	#include <string_view>

	#include "absl/strings/escaping.h"
	#include "gtest/gtest.h"

	#include "aos/json_to_flatbuffer.h"
	#include "aos/json_to_flatbuffer_generated.h"
	#include "flatbuffers/minireflect.h"

	namespace aos {
	namespace testing {

	std::string_view FromFbb(const flatbuffers::FlatBufferBuilder &fbb) {
	return std::string_view(
	reinterpret_cast<const char *>(fbb.GetCurrentBufferPointer()),
	fbb.GetSize());
	}

	std::string_view FromFbb(const flatbuffers::DetachedBuffer &b) {
	return std::string_view(reinterpret_cast<const char *>(b.data()), b.size());
	}

	absl::Span<const uint8_t> ToSpan(const flatbuffers::DetachedBuffer &b) {
	return absl::Span<const uint8_t>(b.data(), b.size());
	}

	class FlatbufferMerge : public ::testing::Test {
	public:
	FlatbufferMerge() {}

	void ExpectMergedOutput(const flatbuffers::DetachedBuffer &fb_merged,
	std::string_view expected_output) {
	ASSERT_NE(fb_merged.size(), 0u);

	const ::std::string merged_output =
	FlatbufferToJson(fb_merged, ConfigurationTypeTable());
	EXPECT_EQ(expected_output, merged_output);

	aos::FlatbufferDetachedBuffer<Configuration> expected_message(
	JsonToFlatbuffer(std::string(expected_output).c_str(),
	ConfigurationTypeTable()));
	EXPECT_TRUE(
	CompareFlatBuffer(flatbuffers::GetRoot<Configuration>(fb_merged.data()),
	&expected_message.message()));
	}

	void JsonMerge(const ::std::string in1, const ::std::string in2,
	const ::std::string out) {
	printf("Merging: %s\n", in1.c_str());
	printf("Merging: %s\n", in2.c_str());
	const flatbuffers::DetachedBuffer fb1 = JsonToFlatbuffer(
	static_cast<const char *>(in1.c_str()), ConfigurationTypeTable());

	const ::std::string in1_nested = "{ \"nested_config\": " + in1 + " }";
	const flatbuffers::DetachedBuffer fb1_nested =
	JsonToFlatbuffer(static_cast<const char *>(in1_nested.c_str()),
	ConfigurationTypeTable());

	const flatbuffers::DetachedBuffer fb2 = JsonToFlatbuffer(
	static_cast<const char *>(in2.c_str()), ConfigurationTypeTable());

	const ::std::string in2_nested = "{ \"nested_config\": " + in2 + " }";
	const flatbuffers::DetachedBuffer fb2_nested =
	JsonToFlatbuffer(static_cast<const char *>(in2_nested.c_str()),
	ConfigurationTypeTable());

	const ::std::string out_nested = "{ \"nested_config\": " + out + " }";

	const flatbuffers::DetachedBuffer empty =
	JsonToFlatbuffer("{ }", ConfigurationTypeTable());

	ASSERT_NE(fb1.size(), 0u);
	ASSERT_NE(fb2.size(), 0u);
	ASSERT_NE(fb1_nested.size(), 0u);
	ASSERT_NE(fb2_nested.size(), 0u);

	// We now want to run 7 tests.
	// in1 merged "" -> in1.
	// in2 merged "" -> in2.
	// "" merged in1 -> in1.
	// "" merged in2 -> in2.
	// nullptr merged in1 -> in1.
	// in1 merged nullptr -> in1.
	// in1 merged in2 -> out.

	{
	// in1 merged with "" => in1.
	flatbuffers::DetachedBuffer fb_merged =
	MergeFlatBuffers<Configuration>(fb1.data(), empty.data());
	ASSERT_NE(fb_merged.size(), 0u);

	EXPECT_EQ(in1, FlatbufferToJson(fb_merged, ConfigurationTypeTable()));
	}

	{
	// in2 merged with "" => in2.
	flatbuffers::DetachedBuffer fb_merged =
	MergeFlatBuffers<Configuration>(fb2.data(), empty.data());
	ASSERT_NE(fb_merged.size(), 0u);

	EXPECT_EQ(in2, FlatbufferToJson(fb_merged, ConfigurationTypeTable()));
	}

	{
	// "" merged with in1 => in1.
	flatbuffers::DetachedBuffer fb_merged =
	MergeFlatBuffers<Configuration>(empty.data(), fb1.data());
	ASSERT_NE(fb_merged.size(), 0u);

	EXPECT_EQ(in1, FlatbufferToJson(fb_merged, ConfigurationTypeTable()));
	}

	{
	// "" merged with in2 => in2.
	flatbuffers::DetachedBuffer fb_merged =
	MergeFlatBuffers<Configuration>(empty.data(), fb2.data());
	ASSERT_NE(fb_merged.size(), 0u);

	EXPECT_EQ(in2, FlatbufferToJson(fb_merged, ConfigurationTypeTable()));
	}

	{
	// nullptr merged with in1 => in1.
	flatbuffers::DetachedBuffer fb_merged =
	MergeFlatBuffers<Configuration>(nullptr, fb1.data());
	ASSERT_NE(fb_merged.size(), 0u);

	EXPECT_EQ(in1, FlatbufferToJson(fb_merged, ConfigurationTypeTable()));
	}

	{
	// in1 merged with nullptr => in1.
	flatbuffers::DetachedBuffer fb_merged =
	MergeFlatBuffers<Configuration>(fb1.data(), nullptr);
	ASSERT_NE(fb_merged.size(), 0u);

	EXPECT_EQ(in1, FlatbufferToJson(fb_merged, ConfigurationTypeTable()));
	}

	{
	// in1 merged with in2 => out.
	flatbuffers::DetachedBuffer fb_merged =
	MergeFlatBuffers<Configuration>(fb1.data(), fb2.data());

	ExpectMergedOutput(fb_merged, out);
	}

	// Test all the different merge methods:
	ExpectMergedOutput(
	MergeFlatBuffers(ConfigurationTypeTable(), fb1.data(), fb2.data()),
	out);
	{
	flatbuffers::FlatBufferBuilder fbb;
	fbb.ForceDefaults(true);
	fbb.Finish(MergeFlatBuffers(
	ConfigurationTypeTable(),
	flatbuffers::GetRoot<flatbuffers::Table>(fb1.data()),
	flatbuffers::GetRoot<flatbuffers::Table>(fb2.data()), &fbb));
	ExpectMergedOutput(fbb.Release(), out);
	}
	{
	flatbuffers::FlatBufferBuilder fbb;
	fbb.ForceDefaults(true);
	fbb.Finish(MergeFlatBuffers<Configuration>(
	flatbuffers::GetRoot<flatbuffers::Table>(fb1.data()),
	flatbuffers::GetRoot<flatbuffers::Table>(fb2.data()), &fbb));
	ExpectMergedOutput(fbb.Release(), out);
	}
	ExpectMergedOutput(MergeFlatBuffers<Configuration>(fb1.data(), fb2.data()),
	out);
	ExpectMergedOutput(MergeFlatBuffers<Configuration>(fb1, fb2), out);
	ExpectMergedOutput(MergeFlatBuffers<Configuration>(
	flatbuffers::GetRoot<Configuration>(fb1.data()),
	flatbuffers::GetRoot<Configuration>(fb2.data()))
	.buffer(),
	out);

	// Now, to make things extra exciting, nest a config inside a config. And
	// run all the tests. This will exercise some fun nested merges and copies.

	{
	// in1_nested merged with "" => in1.
	flatbuffers::DetachedBuffer fb_merged =
	MergeFlatBuffers<Configuration>(fb1_nested.data(), empty.data());
	ASSERT_NE(fb_merged.size(), 0u);

	EXPECT_EQ(in1_nested,
	FlatbufferToJson(fb_merged, ConfigurationTypeTable()));
	}

	{
	// in2_nested merged with "" => in2_nested.
	flatbuffers::DetachedBuffer fb_merged =
	MergeFlatBuffers<Configuration>(fb2_nested.data(), empty.data());
	ASSERT_NE(fb_merged.size(), 0u);

	EXPECT_EQ(in2_nested,
	FlatbufferToJson(fb_merged, ConfigurationTypeTable()));
	}

	{
	// "" merged with in1_nested => in1_nested.
	flatbuffers::DetachedBuffer fb_merged =
	MergeFlatBuffers<Configuration>(empty.data(), fb1_nested.data());
	ASSERT_NE(fb_merged.size(), 0u);

	EXPECT_EQ(in1_nested,
	FlatbufferToJson(fb_merged, ConfigurationTypeTable()));
	}

	{
	// "" merged with in2_nested => in2_nested.
	flatbuffers::DetachedBuffer fb_merged =
	MergeFlatBuffers<Configuration>(empty.data(), fb2_nested.data());
	ASSERT_NE(fb_merged.size(), 0u);

	EXPECT_EQ(in2_nested,
	FlatbufferToJson(fb_merged, ConfigurationTypeTable()));
	}

	{
	// nullptr merged with in1_nested => in1_nested.
	flatbuffers::DetachedBuffer fb_merged =
	MergeFlatBuffers<Configuration>(nullptr, fb1_nested.data());
	ASSERT_NE(fb_merged.size(), 0u);

	EXPECT_EQ(in1_nested,
	FlatbufferToJson(fb_merged, ConfigurationTypeTable()));
	}

	{
	// nullptr merged with in1_nested => in1_nested.
	flatbuffers::DetachedBuffer fb_merged =
	MergeFlatBuffers<Configuration>(fb1_nested.data(), nullptr);
	ASSERT_NE(fb_merged.size(), 0u);

	EXPECT_EQ(in1_nested,
	FlatbufferToJson(fb_merged, ConfigurationTypeTable()));
	}

	{
	// in1_nested merged with in2_nested => out_nested.
	flatbuffers::DetachedBuffer fb_merged =
	MergeFlatBuffers<Configuration>(fb1_nested, fb2_nested);
	ASSERT_NE(fb_merged.size(), 0u);

	EXPECT_EQ(out_nested,
	FlatbufferToJson(fb_merged, ConfigurationTypeTable()));
	}

	// TODO(austin): Try more flatbuffers...
	// Now try copying various flatbuffers and confirming they match.
	{
	flatbuffers::FlatBufferBuilder aos_flatbuffer_copy_fbb;
	aos_flatbuffer_copy_fbb.ForceDefaults(true);

	LOG(INFO) << "Copying " << in1 << " "
	<< absl::BytesToHexString(FromFbb(fb1)) << " at "
	<< reinterpret_cast<const void *>(fb1.data()) << " size "
	<< fb1.size();
	aos_flatbuffer_copy_fbb.Finish(CopyFlatBuffer<Configuration>(
	flatbuffers::GetRoot<Configuration>(fb1.data()),
	&aos_flatbuffer_copy_fbb));

	aos::FlatbufferDetachedBuffer<Configuration> fb_copy(
	aos_flatbuffer_copy_fbb.Release());
	ASSERT_NE(fb_copy.size(), 0u);

	flatbuffers::Verifier v(fb1.data(), fb1.size());
	EXPECT_TRUE(
	v.VerifyTable(flatbuffers::GetRoot<Configuration>(fb1.data())));

	ASSERT_TRUE(fb_copy.Verify()) << in1;

	EXPECT_EQ(in1, FlatbufferToJson(fb_copy));
	}

	{
	flatbuffers::FlatBufferBuilder aos_flatbuffer_copy_message_ptr_fbb;
	aos_flatbuffer_copy_message_ptr_fbb.ForceDefaults(true);

	aos_flatbuffer_copy_message_ptr_fbb.Finish(CopyFlatBuffer<Configuration>(
	flatbuffers::GetRoot<Configuration>(fb2.data()),
	&aos_flatbuffer_copy_message_ptr_fbb));

	aos::FlatbufferDetachedBuffer<Configuration> fb_copy_message_ptr(
	aos_flatbuffer_copy_message_ptr_fbb.Release());
	ASSERT_NE(fb_copy_message_ptr.size(), 0u);

	flatbuffers::FlatBufferBuilder aos_flatbuffer_copy_full_fbb;
	aos_flatbuffer_copy_full_fbb.ForceDefaults(true);

	aos_flatbuffer_copy_full_fbb.Finish(BlindCopyFlatBuffer<Configuration>(
	aos::FlatbufferSpan<Configuration>(ToSpan(fb2)),
	&aos_flatbuffer_copy_full_fbb));

	aos::FlatbufferDetachedBuffer<Configuration> fb_copy_full(
	aos_flatbuffer_copy_full_fbb.Release());
	ASSERT_NE(fb_copy_full.size(), 0u);

	flatbuffers::Verifier v(fb2.data(), fb2.size());
	EXPECT_TRUE(
	v.VerifyTable(flatbuffers::GetRoot<Configuration>(fb2.data())));

	LOG(INFO) << "Verifying copy of " << in2;
	ASSERT_TRUE(fb_copy_message_ptr.Verify()) << in2;
	LOG(INFO) << "Verifying full of " << in2;
	ASSERT_TRUE(fb_copy_full.Verify()) << in2;

	EXPECT_EQ(in2, FlatbufferToJson(fb_copy_message_ptr));
	EXPECT_EQ(in2, FlatbufferToJson(fb_copy_full));
	}

	{
	flatbuffers::FlatBufferBuilder aos_flatbuffer_copy_fbb;
	aos_flatbuffer_copy_fbb.ForceDefaults(true);

	aos_flatbuffer_copy_fbb.Finish(CopyFlatBuffer<Configuration>(
	flatbuffers::GetRoot<Configuration>(fb1_nested.data()),
	&aos_flatbuffer_copy_fbb));

	aos::FlatbufferDetachedBuffer<Configuration> fb_copy(
	aos_flatbuffer_copy_fbb.Release());
	ASSERT_NE(fb_copy.size(), 0u);

	ASSERT_TRUE(fb_copy.Verify());

	EXPECT_EQ(in1_nested, FlatbufferToJson(fb_copy));
	}

	{
	flatbuffers::FlatBufferBuilder aos_flatbuffer_copy_fbb;
	aos_flatbuffer_copy_fbb.ForceDefaults(true);

	aos_flatbuffer_copy_fbb.Finish(CopyFlatBuffer<Configuration>(
	flatbuffers::GetRoot<Configuration>(fb2_nested.data()),
	&aos_flatbuffer_copy_fbb));

	aos::FlatbufferDetachedBuffer<Configuration> fb_copy(
	aos_flatbuffer_copy_fbb.Release());
	ASSERT_NE(fb_copy.size(), 0u);

	ASSERT_TRUE(fb_copy.Verify());

	EXPECT_EQ(in2_nested, FlatbufferToJson(fb_copy));
	}
	}
	};

	// Test the easy ones. Test every type, single, no nesting.
	TEST_F(FlatbufferMerge, Basic) {
	JsonMerge("{ }", "{ }", "{ }");

	JsonMerge("{ \"foo_bool\": true }", "{ \"foo_bool\": false }",
	"{ \"foo_bool\": false }");

	JsonMerge("{ \"foo_bool\": false }", "{ \"foo_bool\": true }",
	"{ \"foo_bool\": true }");

	JsonMerge("{ \"foo_byte\": 5 }", "{ \"foo_byte\": -7 }",
	"{ \"foo_byte\": -7 }");

	JsonMerge("{ \"foo_ubyte\": 5 }", "{ \"foo_ubyte\": 7 }",
	"{ \"foo_ubyte\": 7 }");

	JsonMerge("{ \"foo_short\": 5 }", "{ \"foo_short\": 7 }",
	"{ \"foo_short\": 7 }");

	JsonMerge("{ \"foo_int\": 5 }", "{ \"foo_int\": 7 }", "{ \"foo_int\": 7 }");

	JsonMerge("{ \"foo_uint\": 5 }", "{ \"foo_uint\": 7 }",
	"{ \"foo_uint\": 7 }");

	JsonMerge("{ \"foo_long\": 5 }", "{ \"foo_long\": 7 }",
	"{ \"foo_long\": 7 }");

	JsonMerge("{ \"foo_ulong\": 5 }", "{ \"foo_ulong\": 7 }",
	"{ \"foo_ulong\": 7 }");

	JsonMerge("{ \"foo_float\": 5.0 }", "{ \"foo_float\": 7.1 }",
	"{ \"foo_float\": 7.1 }");

	JsonMerge("{ \"foo_double\": 5.0 }", "{ \"foo_double\": 7.1 }",
	"{ \"foo_double\": 7.1 }");
	}

	// Test arrays of simple types.
	TEST_F(FlatbufferMerge, Array) {
	JsonMerge("{ \"foo_string\": \"baz\" }", "{ \"foo_string\": \"bar\" }",
	"{ \"foo_string\": \"bar\" }");

	JsonMerge("{ \"vector_foo_bool\": [ true, true, false ] }",
	"{ \"vector_foo_bool\": [ false, true, true, false ] }",
	"{ \"vector_foo_bool\": [ true, true, false, false, "
	"true, true, false ] }");

	JsonMerge("{ \"vector_foo_byte\": [ 9, 7, 1 ] }",
	"{ \"vector_foo_byte\": [ -3, 1, 3, 2 ] }",
	"{ \"vector_foo_byte\": [ 9, 7, 1, -3, 1, 3, 2 ] }");

	JsonMerge("{ \"vector_foo_ubyte\": [ 9, 7, 1 ] }",
	"{ \"vector_foo_ubyte\": [ 3, 1, 3, 2 ] }",
	"{ \"vector_foo_ubyte\": [ 9, 7, 1, 3, 1, 3, 2 ] }");

	JsonMerge("{ \"vector_foo_short\": [ 9, 7, 1 ] }",
	"{ \"vector_foo_short\": [ -3, 1, 3, 2 ] }",
	"{ \"vector_foo_short\": [ 9, 7, 1, -3, 1, 3, 2 ] }");

	JsonMerge("{ \"vector_foo_ushort\": [ 9, 7, 1 ] }",
	"{ \"vector_foo_ushort\": [ 3, 1, 3, 2 ] }",
	"{ \"vector_foo_ushort\": [ 9, 7, 1, 3, 1, 3, 2 ] }");

	JsonMerge("{ \"vector_foo_int\": [ 9, 7, 1 ] }",
	"{ \"vector_foo_int\": [ -3, 1, 3, 2 ] }",
	"{ \"vector_foo_int\": [ 9, 7, 1, -3, 1, 3, 2 ] }");

	JsonMerge("{ \"vector_foo_uint\": [ 9, 7, 1 ] }",
	"{ \"vector_foo_uint\": [ 3, 1, 3, 2 ] }",
	"{ \"vector_foo_uint\": [ 9, 7, 1, 3, 1, 3, 2 ] }");

	JsonMerge("{ \"vector_foo_long\": [ 9, 7, 1 ] }",
	"{ \"vector_foo_long\": [ -3, 1, 3, 2 ] }",
	"{ \"vector_foo_long\": [ 9, 7, 1, -3, 1, 3, 2 ] }");

	JsonMerge("{ \"vector_foo_ulong\": [ 9, 7, 1 ] }",
	"{ \"vector_foo_ulong\": [ 3, 1, 3, 2 ] }",
	"{ \"vector_foo_ulong\": [ 9, 7, 1, 3, 1, 3, 2 ] }");

	JsonMerge("{ \"vector_foo_float\": [ 9.0, 7.0, 1.0 ] }",
	"{ \"vector_foo_float\": [ -3.0, 1.3, 3.0, 2.0 ] }",
	"{ \"vector_foo_float\": [ 9.0, 7.0, 1.0, -3.0, 1.3, 3.0, 2.0 ] }");

	JsonMerge(
	"{ \"vector_foo_string\": [ \"9\", \"7\", \"1 \" ] }",
	"{ \"vector_foo_string\": [ \"31\", \"32\" ] }",
	"{ \"vector_foo_string\": [ \"9\", \"7\", \"1 \", \"31\", \"32\" ] }");
	}

	// Test nested messages, and arrays of nested messages.
	TEST_F(FlatbufferMerge, NestedStruct) {
	JsonMerge(
	"{ \"single_application\": { \"name\": \"woot\" } }",
	"{ \"single_application\": { \"name\": \"wow\", \"priority\": 7 } }",
	"{ \"single_application\": { \"name\": \"wow\", \"priority\": 7 } }");

	JsonMerge(
	"{ \"single_application\": { \"name\": \"wow\", \"priority\": 7 } }",
	"{ \"single_application\": { \"name\": \"woot\" } }",
	"{ \"single_application\": { \"name\": \"woot\", \"priority\": 7 } }");

	JsonMerge("{ \"apps\": [ { \"name\": \"woot\" }, { \"name\": \"wow\" } ] }",
	"{ \"apps\": [ { \"name\": \"woo2\" }, { \"name\": \"wo3\" } ] }",
	"{ \"apps\": [ { \"name\": \"woot\" }, { \"name\": \"wow\" }, { "
	"\"name\": \"woo2\" }, { \"name\": \"wo3\" } ] }");
	}

	// Test nested messages, and arrays of nested messages.
	TEST(FlatbufferCopy, WholesaleCopy) {
	flatbuffers::FlatBufferBuilder fbb_expected;
	fbb_expected.ForceDefaults(true);
	fbb_expected.DedupVtables(false);

	{
	flatbuffers::Offset<flatbuffers::String> name1_offset =
	fbb_expected.CreateString("wow");

	std::vector<flatbuffers::Offset<Application>> application_offsets;
	Application::Builder a1_builder(fbb_expected);
	a1_builder.add_name(name1_offset);
	a1_builder.add_priority(7);
	a1_builder.add_long_thingy(0x2549713132LL);
	application_offsets.emplace_back(a1_builder.Finish());

	flatbuffers::Offset<flatbuffers::String> name2_offset =
	fbb_expected.CreateString("foo");
	Application::Builder a2_builder(fbb_expected);
	a2_builder.add_name(name2_offset);
	a2_builder.add_priority(3);
	a2_builder.add_long_thingy(9);
	application_offsets.emplace_back(a2_builder.Finish());

	flatbuffers::Offset<flatbuffers::Vector<flatbuffers::Offset<Application>>>
	applications_offset = fbb_expected.CreateVector(application_offsets);

	Configuration::Builder configuration_builder(fbb_expected);
	configuration_builder.add_apps(applications_offset);
	fbb_expected.Finish(configuration_builder.Finish());
	}

	LOG(INFO) << "Initial alignment " << fbb_expected.GetBufferMinAlignment();

	aos::FlatbufferDetachedBuffer<Configuration> expected(fbb_expected.Release());

	LOG(INFO) << "Expected "
	<< absl::BytesToHexString(std::string_view(
	reinterpret_cast<char *>(expected.span().data()),
	expected.span().size()));

	aos::FlatbufferDetachedBuffer<Application> a1 = []() {
	flatbuffers::FlatBufferBuilder fbb;
	fbb.ForceDefaults(true);

	flatbuffers::Offset<flatbuffers::String> name1_offset =
	fbb.CreateString("wow");

	Application::Builder a1_builder(fbb);
	a1_builder.add_name(name1_offset);
	a1_builder.add_priority(7);
	a1_builder.add_long_thingy(0x2549713132LL);
	flatbuffers::Offset<Application> a1 = a1_builder.Finish();

	fbb.Finish(a1);
	return fbb.Release();
	}();

	aos::FlatbufferDetachedBuffer<Application> a2 =
	JsonToFlatbuffer<Application>(static_cast<const char *>(
	"{ \"name\": \"foo\", \"priority\": 3, \"long_thingy\": 9 }"));

	aos::FlatbufferDetachedBuffer<Configuration> c1 = [&a1, &a2]() {
	flatbuffers::FlatBufferBuilder fbb;
	fbb.ForceDefaults(true);

	std::vector<flatbuffers::Offset<Application>> application_offsets;
	application_offsets.emplace_back(BlindCopyFlatBuffer(a1, &fbb));
	application_offsets.emplace_back(BlindCopyFlatBuffer(a2, &fbb));

	flatbuffers::Offset<flatbuffers::Vector<flatbuffers::Offset<Application>>>
	applications_offset = fbb.CreateVector(application_offsets);

	Configuration::Builder configuration_builder(fbb);
	configuration_builder.add_apps(applications_offset);
	fbb.Finish(configuration_builder.Finish());

	return fbb.Release();
	}();

	LOG(INFO) << "Got "
	<< absl::BytesToHexString(
	std::string_view(reinterpret_cast<char *>(c1.span().data()),
	c1.span().size()));

	aos::FlatbufferDetachedBuffer<Configuration> c2 = [&a1, &a2]() {
	flatbuffers::FlatBufferBuilder fbb;
	fbb.ForceDefaults(true);

	std::vector<flatbuffers::Offset<Application>> application_offsets;
	application_offsets.emplace_back(CopyFlatBuffer(&a1.message(), &fbb));
	application_offsets.emplace_back(CopyFlatBuffer(&a2.message(), &fbb));

	flatbuffers::Offset<flatbuffers::Vector<flatbuffers::Offset<Application>>>
	applications_offset = fbb.CreateVector(application_offsets);

	Configuration::Builder configuration_builder(fbb);
	configuration_builder.add_apps(applications_offset);
	fbb.Finish(configuration_builder.Finish());

	return fbb.Release();
	}();

	LOG(INFO) << "Got "
	<< absl::BytesToHexString(
	std::string_view(reinterpret_cast<char *>(c2.span().data()),
	c2.span().size()));

	ASSERT_TRUE(expected.Verify());
	ASSERT_TRUE(c1.Verify());
	ASSERT_TRUE(c2.Verify());

	LOG(INFO) << FlatbufferToJson(expected);
	LOG(INFO) << FlatbufferToJson(c1);
	LOG(INFO) << FlatbufferToJson(c2);
	EXPECT_EQ(FlatbufferToJson(expected), FlatbufferToJson(c1));
	EXPECT_EQ(FlatbufferToJson(expected), FlatbufferToJson(c2));
	}

	// Tests a compare of 2 basic (different) messages.
	TEST_F(FlatbufferMerge, CompareDifferent) {
	aos::FlatbufferDetachedBuffer<Configuration> message1(JsonToFlatbuffer(
	"{ \"single_application\": { \"name\": \"wow\", \"priority\": 7 } }",
	ConfigurationTypeTable()));
	aos::FlatbufferDetachedBuffer<Configuration> message2(JsonToFlatbuffer(
	"{ \"single_application\": { \"name\": \"wow\", \"priority\": 8 } }",
	ConfigurationTypeTable()));

	EXPECT_FALSE(CompareFlatBuffer(&message1.message(), &message2.message()));
	}

	// TODO(austin): enums
	// TODO(austin): unions
	// TODO(austin): struct

	} // namespace testing
	} // namespace aos