Switch TestReliableMessageProtocol to async message delivery (#13099)

* Convert TestReliableMessageProtocol to using LoopbackMessagingContext.

* Use async message delivery in TestReliableMessageProtocol.

src/app/tests/AppTestContext.h

@@ -25,9 +25,9 @@ namespace Test {
  * @brief The context of test cases for messaging layer. It wil initialize network layer and system layer, and create
  *        two secure sessions, connected with each other. Exchanges can be created for each secure session.
  */
-class AppContext : public LoopbackMessagingContext<LoopbackTransport>
+class AppContext : public LoopbackMessagingContext<>
 {
-    typedef LoopbackMessagingContext<LoopbackTransport> Super;
+    typedef LoopbackMessagingContext<> Super;
 
 public:
     /// Initialize the underlying layers.

src/messaging/tests/MessagingContext.cpp

@@ -29,6 +29,7 @@ CHIP_ERROR MessagingContext::Init(TransportMgrBase * transport, IOContext * ioCo
     mInitialized = true;
 
     mIOContext = ioContext;
+    mTransport = transport;
 
     ReturnErrorOnFailure(mSessionManager.Init(&GetSystemLayer(), transport, &mMessageCounterManager));
 
@@ -56,6 +57,20 @@ CHIP_ERROR MessagingContext::Shutdown()
     return CHIP_NO_ERROR;
 }
 
+CHIP_ERROR MessagingContext::InitFromExisting(const MessagingContext & existing)
+{
+    return Init(existing.mTransport, existing.mIOContext);
+}
+
+CHIP_ERROR MessagingContext::ShutdownAndRestoreExisting(MessagingContext & existing)
+{
+    CHIP_ERROR err = Shutdown();
+    // Point the transport back to the original session manager, since we had
+    // pointed it to ours.
+    existing.mTransport->SetSessionManager(&existing.GetSecureSessionManager());
+    return err;
+}
+
 SessionHandle MessagingContext::GetSessionBobToAlice()
 {
     return mSessionBobToAlice.Get();

src/messaging/tests/MessagingContext.h

@@ -50,6 +50,14 @@ class MessagingContext
     // Shutdown all layers, finalize operations
     CHIP_ERROR Shutdown();
 
+    // Initialize from an existing messaging context.  Useful if we want to
+    // share some state (like the transport).
+    CHIP_ERROR InitFromExisting(const MessagingContext & existing);
+
+    // The shutdown method to use if using InitFromExisting.  Must pass in the
+    // same existing context as was passed to InitFromExisting.
+    CHIP_ERROR ShutdownAndRestoreExisting(MessagingContext & existing);
+
     static Inet::IPAddress GetAddress()
     {
         Inet::IPAddress addr;
@@ -98,6 +106,7 @@ class MessagingContext
     Messaging::ExchangeManager mExchangeManager;
     secure_channel::MessageCounterManager mMessageCounterManager;
     IOContext * mIOContext;
+    TransportMgrBase * mTransport; // Only needed for InitFromExisting.
 
     NodeId mBobNodeId       = 123654;
     NodeId mAliceNodeId     = 111222333;
@@ -115,7 +124,7 @@ class MessagingContext
     FabricIndex mDestFabricIndex = 0;
 };
 
-template <typename Transport>
+template <typename Transport = LoopbackTransport>
 class LoopbackMessagingContext : public MessagingContext
 {
 public:
@@ -166,6 +175,8 @@ class LoopbackMessagingContext : public MessagingContext
 
     Transport & GetLoopback() { return mTransportManager.GetTransport().template GetImplAtIndex<0>(); }
 
+    TransportMgrBase & GetTransportMgr() { return mTransportManager; }
+
     /*
      * For unit-tests that simulate end-to-end transmission and reception of messages in loopback mode,
      * this mode better replicates a real-functioning stack that correctly handles the processing

src/messaging/tests/TestExchangeMgr.cpp

@@ -49,7 +49,7 @@ using namespace chip::Inet;
 using namespace chip::Transport;
 using namespace chip::Messaging;
 
-using TestContext = chip::Test::LoopbackMessagingContext<Test::LoopbackTransport>;
+using TestContext = Test::LoopbackMessagingContext<>;
 
 enum : uint8_t
 {