These cover the various LLCPP “message” classes and utilities, which are responsible for encoding/decoding FIDL values and sometimes allocating storage for them:
fidl::EncodedMessagefidl::OutgoingMessagefidl::OutgoingToEncodedMessagefidl::internal::OwnedEncodedMessage<Foo>fidl::internal::UnownedEncodedMessage<Foo>In addition, the fidl::Status result/error types are also tested here, since a major use case is them being composed by message container types.
Types and utilities responsible for message storage and buffer allocation are also tested here, since they're typically used as part of message containers.