These cover the various LLCPP “message” classes and utilities, which are responsible for encoding/decoding FIDL values and sometimes allocating storage for them:
fidl::IncomingMessagefidl::OutgoingMessagefidl::OutgoingMessagefidl::OutgoingIovecMessagefidl::OwnedEncodedMessage<Foo>fidl::UnownedEncodedMessage<Foo>fidl::OutgoingToIncomingMessageIn addition, the fidl::Result result/error types are also tested here, since a major use case is them being composed by message container types.