public void TestRecoverMissingExtensions()
{
const int optionalInt32 = 12345678;
TestAllExtensions.Builder builder = TestAllExtensions.CreateBuilder();
builder.SetExtension(Unittest.OptionalInt32Extension, optionalInt32);
builder.AddExtension(Unittest.RepeatedDoubleExtension, 1.1);
builder.AddExtension(Unittest.RepeatedDoubleExtension, 1.2);
builder.AddExtension(Unittest.RepeatedDoubleExtension, 1.3);
TestAllExtensions msg = builder.Build();
Assert.IsTrue(msg.HasExtension(Unittest.OptionalInt32Extension));
Assert.AreEqual(3, msg.GetExtensionCount(Unittest.RepeatedDoubleExtension));
byte[] bits = msg.ToByteArray();
TestAllExtensions copy = TestAllExtensions.ParseFrom(bits);
Assert.IsFalse(copy.HasExtension(Unittest.OptionalInt32Extension));
Assert.AreEqual(0, copy.GetExtensionCount(Unittest.RepeatedDoubleExtension));
Assert.AreNotEqual(msg, copy);
//Even though copy does not understand the typees they serialize correctly
byte[] copybits = copy.ToByteArray();
Assert.AreEqual(bits, copybits);
ExtensionRegistry registry = ExtensionRegistry.CreateInstance();
Unittest.RegisterAllExtensions(registry);
//Now we can take those copy bits and restore the full message with extensions
copy = TestAllExtensions.ParseFrom(copybits, registry);
Assert.IsTrue(copy.HasExtension(Unittest.OptionalInt32Extension));
Assert.AreEqual(3, copy.GetExtensionCount(Unittest.RepeatedDoubleExtension));
Assert.AreEqual(msg, copy);
Assert.AreEqual(bits, copy.ToByteArray());
//If we modify the object this should all continue to work as before
copybits = copy.ToBuilder().Build().ToByteArray();
Assert.AreEqual(bits, copybits);
//If we replace extension the object this should all continue to work as before
copybits = copy.ToBuilder()
.SetExtension(Unittest.OptionalInt32Extension, optionalInt32)
.Build().ToByteArray();
Assert.AreEqual(bits, copybits);
}