diff --git a/aos/testing/test_logging.cc b/aos/testing/test_logging.cc
index fa70d47..bc60081 100644
--- a/aos/testing/test_logging.cc
+++ b/aos/testing/test_logging.cc
@@ -20,6 +20,22 @@
  public:
   const ::std::vector<LogMessage> &messages() { return messages_; }
 
+  // Sets the current thread's time to be monotonic_now for logging.
+  void MockTime(::aos::monotonic_clock::time_point monotonic_now) {
+    mock_time_ = true;
+    monotonic_now_ = monotonic_now;
+  }
+
+  // Clears any mock time for the current thread.
+  void UnMockTime() { mock_time_ = false; }
+
+  ::aos::monotonic_clock::time_point monotonic_now() const override {
+    if (mock_time_) {
+      return monotonic_now_;
+    }
+    return ::aos::monotonic_clock::now();
+  }
+
   // This class has to be a singleton so that everybody can get access to the
   // same instance to read out the messages etc.
   static TestLogImplementation *GetInstance() {
@@ -80,10 +96,20 @@
   bool print_as_messages_come_in_ = false;
   FILE *output_file_ = stdout;
   ::aos::Mutex messages_mutex_;
+
+  // Thread local storage for mock time.  This is thread local because if
+  // someone spawns a thread and goes to town in parallel with a simulated event
+  // loop, we want to just print the actual monotonic clock out.
+  static thread_local bool mock_time_;
+  static thread_local ::aos::monotonic_clock::time_point monotonic_now_;
 };
 
+thread_local bool TestLogImplementation::mock_time_ = false;
+thread_local ::aos::monotonic_clock::time_point
+    TestLogImplementation::monotonic_now_ = ::aos::monotonic_clock::min_time;
+
 class MyTestEventListener : public ::testing::EmptyTestEventListener {
-  virtual void OnTestStart(const ::testing::TestInfo &/*test_info*/) {
+  virtual void OnTestStart(const ::testing::TestInfo & /*test_info*/) {
     TestLogImplementation::GetInstance()->ClearMessages();
   }
   virtual void OnTestEnd(const ::testing::TestInfo &test_info) {
@@ -141,5 +167,12 @@
   TestLogImplementation::GetInstance()->PrintMessagesAsTheyComeIn();
 }
 
+void MockTime(::aos::monotonic_clock::time_point monotonic_now) {
+  TestLogImplementation::GetInstance()->MockTime(monotonic_now);
+}
+void UnMockTime() {
+  TestLogImplementation::GetInstance()->UnMockTime();
+}
+
 }  // namespace testing
 }  // namespace aos