Class Cap

tests/host/ipc/ipc_client_test.cpp:122–133

// Captures the bytes a MessageComposer would send, without a real socket.
static std::vector<std::byte> frame(const MessageComposer& c) {
    struct Cap final : ITransport {
        std::vector<std::byte> b;
        void send(std::span<const std::byte> d) override {
            b.assign(d.begin(), d.end());
        }
        std::size_t receive(std::span<std::byte>) override {
            return 0;
        }
        bool has_data() const override {
            return false;
        }
    };
    Cap cap;
    c.send(cap);
    return cap.b;