Fix event logging test for platforms using system time (#27114)

* Fix event logging test for platforms using system time

Using UTC (epoch) vs system relative time in the event logging affects
the size of TLV-encoded events. This has to be accounted for in the unit
test otherwise the test might fail without apparent reasons.

* Apply suggestions from code review

Co-authored-by: Boris Zbarsky <bzbarsky@apple.com>

---------

Co-authored-by: Boris Zbarsky <bzbarsky@apple.com>

src/app/EventManagement.cpp

@@ -173,7 +173,7 @@ CHIP_ERROR EventManagement::EnsureSpaceInCircularBuffer(size_t aRequiredSpace, P
 
  // Check that we have this much space in all our event buffers that might
  // hold the event. If we do not, that will prevent the event from being
- // properly evicted into higher-priority bufers.  We want to discover
+ // properly evicted into higher-priority buffers. We want to discover
  // this early, so that testing surfaces the need to make those buffers
  // larger.
  for (auto * currentBuffer = mpEventBuffer; currentBuffer; currentBuffer = currentBuffer->GetNextCircularEventBuffer())

src/app/EventManagement.h

@@ -399,9 +399,9 @@ class EventManagement
  int mFieldsToRead = 0;
  /* PriorityLevel and DeltaTime are there if that is not first event when putting events in report*/
 #if CHIP_DEVICE_CONFIG_EVENT_LOGGING_UTC_TIMESTAMPS
- Timestamp mCurrentTime = Timestamp::System(System::Clock::kZero);
-#else // CHIP_DEVICE_CONFIG_EVENT_LOGGING_UTC_TIMESTAMPS
  Timestamp mCurrentTime = Timestamp::Epoch(System::Clock::kZero);
+#else // CHIP_DEVICE_CONFIG_EVENT_LOGGING_UTC_TIMESTAMPS
+ Timestamp mCurrentTime = Timestamp::System(System::Clock::kZero);
 #endif // CHIP_DEVICE_CONFIG_EVENT_LOGGING_UTC_TIMESTAMPS
  PriorityLevel mPriority = PriorityLevel::First;
  ClusterId mClusterId = 0;

src/app/tests/TestEventLogging.cpp

@@ -55,9 +55,9 @@ static const chip::EndpointId kTestEndpointId1 = 2;
 static const chip::EndpointId kTestEndpointId2 = 3;
 static const chip::TLV::Tag kLivenessDeviceStatus = chip::TLV::ContextTag(1);
 
-static uint8_t gDebugEventBuffer[128];
-static uint8_t gInfoEventBuffer[128];
-static uint8_t gCritEventBuffer[128];
+static uint8_t gDebugEventBuffer[120];
+static uint8_t gInfoEventBuffer[120];
+static uint8_t gCritEventBuffer[120];
 static chip::app::CircularEventBuffer gCircularEventBuffer[3];
 
 class TestContext : public chip::Test::AppContext
@@ -154,6 +154,15 @@ static void CheckLogReadOut(nlTestSuite * apSuite, chip::app::EventManagement &
  err = alogMgmt.FetchEventsSince(writer, clusterInfo, startingEventNumber, eventCount, chip::Access::SubjectDescriptor{});
  NL_TEST_ASSERT(apSuite, err == CHIP_NO_ERROR || err == CHIP_END_OF_TLV);
 
+ auto eventTLVSize = writer.GetLengthWritten() / eventCount;
+ // XXX: Make sure that the sizes of our event storages are big enough to hold at least 3 events
+ // but small enough not to hold 4 events. It is very important to check this because of the
+ // hard-coded logic of this unit test.
+ // The size of TLV-encoded event can vary depending on the UTC vs system time controlled by
+ // the CHIP_DEVICE_CONFIG_EVENT_LOGGING_UTC_TIMESTAMPS, because the relative system time
+ // will be most likely encoded in 1 byte, while the UTC time will be encoded in 8 bytes.
+ NL_TEST_ASSERT(apSuite, sizeof(gDebugEventBuffer) >= eventTLVSize * 3 && sizeof(gDebugEventBuffer) < eventTLVSize * 4);
+
  reader.Init(backingStore.Get(), writer.GetLengthWritten());
 
  err = chip::TLV::Utilities::Count(reader, totalNumElements, false);
@@ -307,22 +316,19 @@ static void CheckLogEventWithDiscardLowEvent(nlTestSuite * apSuite, void * apCon
  NL_TEST_ASSERT(apSuite, err == CHIP_NO_ERROR);
  CheckLogState(apSuite, logMgmt, 3, chip::app::PriorityLevel::Debug);
 }
-/**
- * Test Suite. It lists all the test functions.
- */
 
-const nlTest sTests[] = { NL_TEST_DEF("CheckLogEventWithEvictToNextBuffer", CheckLogEventWithEvictToNextBuffer),
- NL_TEST_DEF("CheckLogEventWithDiscardLowEvent", CheckLogEventWithDiscardLowEvent), NL_TEST_SENTINEL() };
+const nlTest sTests[] = {
+ NL_TEST_DEF("CheckLogEventWithEvictToNextBuffer", CheckLogEventWithEvictToNextBuffer),
+ NL_TEST_DEF("CheckLogEventWithDiscardLowEvent", CheckLogEventWithDiscardLowEvent),
+ NL_TEST_SENTINEL(),
+};
 
-// clang-format off
-nlTestSuite sSuite =
-{
+nlTestSuite sSuite = {
  "EventLogging",
  &sTests[0],
  TestContext::Initialize,
- TestContext::Finalize
+ TestContext::Finalize,
 };
-// clang-format on
 
 } // namespace