[Client] Unit test LagMonitor stall recording

Drives recordGap() directly to cover the threshold, plausibility cap,
trim, and clear behavior without timing-dependent waits.

Took 36 seconds

cockatrice/src/client/lag_monitor.h

@@ -41,7 +41,8 @@ public:
     struct StallRecord
     {
         qint64 timestampMsSinceEpoch = 0; ///< when the stalled period ended
-        qint64 durationMs = 0;            ///< approximate length of the freeze; measured tick to tick, so it can exceed the true stall by up to TICK_INTERVAL_MS
+        qint64 durationMs = 0; ///< approximate length of the freeze; measured tick to tick, so it can exceed the true
+                               ///< stall by up to TICK_INTERVAL_MS
     };
 
     static constexpr int TICK_INTERVAL_MS = 500;

tests/CMakeLists.txt

@@ -12,6 +12,7 @@ add_test(NAME server_card_counter_test COMMAND server_card_counter_test)
 add_test(NAME server_counter_test COMMAND server_counter_test)
 add_test(NAME server_rate_limiter_test COMMAND server_rate_limiter_test)
 add_test(NAME warning_categories_test COMMAND warning_categories_test)
+add_test(NAME lag_monitor_test COMMAND lag_monitor_test)
 add_test(NAME latency_tracker_test COMMAND latency_tracker_test)
 
 add_test(NAME deck_hash_performance_test COMMAND deck_hash_performance_test)
@@ -30,6 +31,8 @@ add_executable(server_card_counter_test server_card_counter_test.cpp)
 add_executable(server_counter_test server_counter_test.cpp)
 add_executable(server_rate_limiter_test server_rate_limiter_test.cpp)
 add_executable(warning_categories_test warning_categories_test.cpp)
+add_executable(lag_monitor_test ${CMAKE_SOURCE_DIR}/cockatrice/src/client/lag_monitor.cpp lag_monitor_test.cpp)
+target_include_directories(lag_monitor_test PRIVATE ${CMAKE_SOURCE_DIR}/cockatrice/src)
 add_executable(latency_tracker_test latency_tracker_test.cpp)
 
 find_package(GTest)
@@ -68,6 +71,7 @@ if(NOT GTEST_FOUND)
   add_dependencies(server_counter_test gtest)
   add_dependencies(server_rate_limiter_test gtest)
   add_dependencies(warning_categories_test gtest)
+  add_dependencies(lag_monitor_test gtest)
   add_dependencies(latency_tracker_test gtest)
 endif()
 
@@ -103,6 +107,7 @@ target_link_libraries(
 target_link_libraries(
   warning_categories_test libcockatrice_utility Threads::Threads ${GTEST_BOTH_LIBRARIES} ${TEST_QT_MODULES}
 )
+target_link_libraries(lag_monitor_test Threads::Threads ${GTEST_BOTH_LIBRARIES} ${TEST_QT_MODULES})
 target_link_libraries(
   latency_tracker_test libcockatrice_network Threads::Threads ${GTEST_BOTH_LIBRARIES} ${TEST_QT_MODULES}
 )

tests/lag_monitor_test.cpp

@@ -0,0 +1,103 @@
+#include "client/lag_monitor.h"
+
+#include <QCoreApplication>
+#include <QDateTime>
+#include <QEvent>
+#include <QLoggingCategory>
+#include <gtest/gtest.h>
+
+namespace
+{
+
+/// Timestamps are taken at recording time; allow generous scheduler slack.
+constexpr qint64 TIMESTAMP_SLACK_MS = 10000;
+
+} // namespace
+
+class LagMonitorTest : public ::testing::Test
+{
+protected:
+    LagMonitor monitor;
+};
+
+TEST_F(LagMonitorTest, GapAtOrBelowThresholdIsIgnored)
+{
+    monitor.recordGap(0);
+    monitor.recordGap(LagMonitor::TICK_INTERVAL_MS);
+    monitor.recordGap(LagMonitor::STALL_THRESHOLD_MS);
+
+    EXPECT_TRUE(monitor.recentStalls().isEmpty());
+}
+
+TEST_F(LagMonitorTest, GapAboveThresholdIsRecorded)
+{
+    monitor.recordGap(LagMonitor::STALL_THRESHOLD_MS + 1);
+
+    const QList<LagMonitor::StallRecord> stalls = monitor.recentStalls();
+    ASSERT_EQ(1, stalls.size());
+    EXPECT_EQ(LagMonitor::STALL_THRESHOLD_MS + 1, stalls.first().durationMs);
+}
+
+TEST_F(LagMonitorTest, RecordedTimestampIsFresh)
+{
+    monitor.recordGap(LagMonitor::STALL_THRESHOLD_MS + 1);
+
+    const qint64 now = QDateTime::currentMSecsSinceEpoch();
+    ASSERT_EQ(1, monitor.recentStalls().size());
+    EXPECT_LE(qAbs(monitor.recentStalls().first().timestampMsSinceEpoch - now), TIMESTAMP_SLACK_MS);
+}
+
+TEST_F(LagMonitorTest, RecordsAreTrimmedToMaxOldestFirst)
+{
+    for (int i = 0; i < LagMonitor::MAX_RECORDED_STALLS + 5; ++i) {
+        monitor.recordGap(LagMonitor::STALL_THRESHOLD_MS + 1 + i);
+    }
+
+    const QList<LagMonitor::StallRecord> stalls = monitor.recentStalls();
+    ASSERT_EQ(LagMonitor::MAX_RECORDED_STALLS, stalls.size());
+    EXPECT_EQ(LagMonitor::STALL_THRESHOLD_MS + 6, stalls.first().durationMs);
+    EXPECT_EQ(LagMonitor::STALL_THRESHOLD_MS + 5 + LagMonitor::MAX_RECORDED_STALLS, stalls.last().durationMs);
+}
+
+TEST_F(LagMonitorTest, GapAtPlausibilityCapIsKept)
+{
+    monitor.recordGap(LagMonitor::MAX_PLAUSIBLE_STALL_MS);
+
+    ASSERT_EQ(1, monitor.recentStalls().size());
+    EXPECT_EQ(LagMonitor::MAX_PLAUSIBLE_STALL_MS, monitor.recentStalls().first().durationMs);
+}
+
+TEST_F(LagMonitorTest, GapBeyondPlausibilityCapIsDropped)
+{
+    monitor.recordGap(LagMonitor::MAX_PLAUSIBLE_STALL_MS + 1);
+
+    EXPECT_TRUE(monitor.recentStalls().isEmpty());
+}
+
+TEST_F(LagMonitorTest, ClearStallsEmptiesList)
+{
+    monitor.recordGap(LagMonitor::STALL_THRESHOLD_MS + 1);
+    ASSERT_EQ(1, monitor.recentStalls().size());
+
+    monitor.clearStalls();
+
+    EXPECT_TRUE(monitor.recentStalls().isEmpty());
+}
+
+TEST_F(LagMonitorTest, ApplicationStateChangeDoesNotRecordAStall)
+{
+    QObject probe;
+    QEvent event(QEvent::ApplicationStateChange);
+
+    QCoreApplication::sendEvent(&probe, &event);
+
+    EXPECT_TRUE(monitor.recentStalls().isEmpty());
+}
+
+int main(int argc, char **argv)
+{
+    QLoggingCategory::setFilterRules("lag_monitor.*=false");
+    QCoreApplication app(argc, argv);
+    ::testing::InitGoogleTest(&argc, argv);
+    return RUN_ALL_TESTS();
+}