Fix failing TestTimedHandler unit test.

This is failing due to a merge conflict between
project-chip#11988 and
project-chip#12389: the latter
ends up in an error state as described in
project-chip#12466 (comment)
and the former makes our code a lot more sensitive to being in that
error state.

The fix for the test is to not use the sync mode of loopback
transport, which allows the stack for sending a message to unwind
before responses are delivered and avoids the "object deleted by
response while we are still working with it" problem described in
project-chip#12466 (comment).

When the responses were made async, it turned out the test was missing
some "expect response" flags that should have been there all along and
it was only passing because the response happened before the send
could get to the "close the exchange" stage.  With async responses,
exchanges were closing too early without the "expect response" flags.

Separately we should figure out which parts of
project-chip#12466 we should
do.

src/app/TimedHandler.cpp

@@ -17,6 +17,7 @@
  */
 
 #include "TimedHandler.h"
+#include <app/InteractionModelDelegate.h>
 #include <app/InteractionModelEngine.h>
 #include <app/MessageDef/TimedRequestMessage.h>
 #include <app/StatusResponse.h>
@@ -122,10 +123,13 @@ CHIP_ERROR TimedHandler::HandleTimedRequestAction(Messaging::ExchangeContext * a
 
     ChipLogDetail(DataManagement, "Got Timed Request with timeout %" PRIu16 ": handler %p exchange " ChipLogFormatExchange,
                   timeoutMs, this, ChipLogValueExchange(aExchangeContext));
-    // Tell the exchange to close after the timeout passes, so we don't get
-    // stuck waiting forever if the client never sends another message.
+    // Use at least our default IM timeout, because if we close our exchange as
+    // soon as we know the delay has passed we won't be able to send the
+    // UNSUPPORTED_ACCESS status code the spec tells us to send (and in fact
+    // will send nothing and the other side will have to time out to realize
+    // it's missed its window).
     auto delay = System::Clock::Milliseconds32(timeoutMs);
-    aExchangeContext->SetResponseTimeout(delay);
+    aExchangeContext->SetResponseTimeout(std::max(delay, kImMessageTimeout));
     ReturnErrorOnFailure(StatusResponse::Send(Status::Success, aExchangeContext, /* aExpectResponse = */ true));
 
     // Now just wait for the client.

src/app/tests/TestTimedHandler.cpp

@@ -124,6 +124,8 @@ void TestTimedHandler::TestFollowingMessageFastEnough(nlTestSuite * aSuite, void
 
     CHIP_ERROR err = exchange->SendMessage(MsgType::TimedRequest, std::move(payload), SendMessageFlags::kExpectResponse);
     NL_TEST_ASSERT(aSuite, err == CHIP_NO_ERROR);
+
+    ctx.DrainAndServiceIO();
     NL_TEST_ASSERT(aSuite, delegate.mNewMessageReceived);
     NL_TEST_ASSERT(aSuite, delegate.mLastMessageWasStatus);
     NL_TEST_ASSERT(aSuite, delegate.mStatus.mStatus == Status::Success);
@@ -136,8 +138,10 @@ void TestTimedHandler::TestFollowingMessageFastEnough(nlTestSuite * aSuite, void
     delegate.mKeepExchangeOpen   = false;
     delegate.mNewMessageReceived = false;
 
-    err = exchange->SendMessage(aMsgType, std::move(payload));
+    err = exchange->SendMessage(aMsgType, std::move(payload), SendMessageFlags::kExpectResponse);
     NL_TEST_ASSERT(aSuite, err == CHIP_NO_ERROR);
+
+    ctx.DrainAndServiceIO();
     NL_TEST_ASSERT(aSuite, delegate.mNewMessageReceived);
     NL_TEST_ASSERT(aSuite, delegate.mLastMessageWasStatus);
     NL_TEST_ASSERT(aSuite, delegate.mStatus.mStatus != Status::UnsupportedAccess);
@@ -170,6 +174,8 @@ void TestTimedHandler::TestFollowingMessageTooSlow(nlTestSuite * aSuite, void *
 
     CHIP_ERROR err = exchange->SendMessage(MsgType::TimedRequest, std::move(payload), SendMessageFlags::kExpectResponse);
     NL_TEST_ASSERT(aSuite, err == CHIP_NO_ERROR);
+
+    ctx.DrainAndServiceIO();
     NL_TEST_ASSERT(aSuite, delegate.mNewMessageReceived);
     NL_TEST_ASSERT(aSuite, delegate.mLastMessageWasStatus);
     NL_TEST_ASSERT(aSuite, delegate.mStatus.mStatus == Status::Success);
@@ -185,8 +191,10 @@ void TestTimedHandler::TestFollowingMessageTooSlow(nlTestSuite * aSuite, void *
     delegate.mKeepExchangeOpen   = false;
     delegate.mNewMessageReceived = false;
 
-    err = exchange->SendMessage(aMsgType, std::move(payload));
+    err = exchange->SendMessage(aMsgType, std::move(payload), SendMessageFlags::kExpectResponse);
     NL_TEST_ASSERT(aSuite, err == CHIP_NO_ERROR);
+
+    ctx.DrainAndServiceIO();
     NL_TEST_ASSERT(aSuite, delegate.mNewMessageReceived);
     NL_TEST_ASSERT(aSuite, delegate.mLastMessageWasStatus);
     NL_TEST_ASSERT(aSuite, delegate.mStatus.mStatus == Status::UnsupportedAccess);
@@ -217,6 +225,8 @@ void TestTimedHandler::TestInvokeNeverComes(nlTestSuite * aSuite, void * aContex
 
     CHIP_ERROR err = exchange->SendMessage(MsgType::TimedRequest, std::move(payload), SendMessageFlags::kExpectResponse);
     NL_TEST_ASSERT(aSuite, err == CHIP_NO_ERROR);
+
+    ctx.DrainAndServiceIO();
     NL_TEST_ASSERT(aSuite, delegate.mNewMessageReceived);
     NL_TEST_ASSERT(aSuite, delegate.mLastMessageWasStatus);
     NL_TEST_ASSERT(aSuite, delegate.mStatus.mStatus == Status::Success);
@@ -249,7 +259,7 @@ nlTestSuite sSuite =
 {
     "TestTimedHandler",
     &sTests[0],
-    TestContext::Initialize,
+    TestContext::InitializeAsync,
     TestContext::Finalize
 };
 // clang-format on