fix(libsinsp): fix failing UT THRD_TABLE_remove_inactive_threads

Force reset of last_access_time in remove_inactive_threads method of
sinsp_with_test_input.

Signed-off-by: irozzo-1A <iacopo@sysdig.com>

Author: irozzo-1A

userspace/libsinsp/sinsp.h

@@ -782,6 +782,9 @@ class SINSP_PUBLIC sinsp : public capture_stats_source {
 
 	uint64_t get_lastevent_ts() const { return m_timestamper.get_cached_ts(); }
 	void set_lastevent_ts(const uint64_t v) { m_timestamper.set_cached_ts(v); }
+	/** Reset cached last-event timestamp so a subsequent set_lastevent_ts can set any value (e.g.
+	 * in tests). */
+	void reset_lastevent_ts() { m_timestamper.reset(); }
 
 	inline const std::string& get_host_root() const { return m_host_root; }
 	inline void set_host_root(const std::string& s) { m_host_root = s; }

userspace/libsinsp/test/sinsp_with_test_input.cpp

@@ -703,6 +703,10 @@ void sinsp_with_test_input::remove_inactive_threads(uint64_t m_lastevent_ts,
 	m_inspector.m_thread_manager->set_last_flush_time_ns(1);
 	m_inspector.m_threads_purging_scan_time_ns = 2;
 
+	// set_lastevent_ts only updates when the new value is greater than the current (monotonic).
+	// After processing events, the cached ts is the last event ts (e.g. from increasing_ts()).
+	// Reset so the test can force the "current time" used by the purge logic.
+	m_inspector.reset_lastevent_ts();
 	m_inspector.set_lastevent_ts(m_lastevent_ts);
 	m_inspector.m_thread_timeout_ns = thread_timeout;
 	m_inspector.remove_inactive_threads();