diff --git a/selfdrive/loggerd/SConscript b/selfdrive/loggerd/SConscript
index 0d3fe55048..2adcfb846c 100644
--- a/selfdrive/loggerd/SConscript
+++ b/selfdrive/loggerd/SConscript
@@ -7,7 +7,7 @@ libs = [logger_lib, common, cereal, messaging, visionipc,
         'avformat', 'avcodec', 'swscale', 'avutil',
         'yuv', 'bz2', 'OpenCL']
 
-src = ['main.cc', 'loggerd.cc']
+src = ['loggerd.cc']
 if arch in ["aarch64", "larch64"]:
   src += ['omx_encoder.cc']
   libs += ['OmxCore', 'gsl', 'CB'] + gpucommon
@@ -24,8 +24,8 @@ if arch == "Darwin":
   del libs[libs.index('OpenCL')]
   env['FRAMEWORKS'] = ['OpenCL']
 
-env.Program('loggerd', src, LIBS=libs)
+env.Program('loggerd', ['main.cc'] + src, LIBS=libs)
 env.Program('bootlog.cc', LIBS=libs)
 
 if GetOption('test'):
-  env.Program('tests/test_logger', ['tests/test_runner.cc', 'tests/test_logger.cc', env.Object('logger_util', '#/selfdrive/ui/replay/util.cc')], LIBS=[libs] + ['curl', 'crypto'])
+  env.Program('tests/test_logger', ['tests/test_runner.cc', 'tests/test_loggerd.cc', 'tests/test_logger.cc', env.Object('logger_util', '#/selfdrive/ui/replay/util.cc')] + src, LIBS=[libs] + ['curl', 'crypto', 'bz2'])
diff --git a/selfdrive/loggerd/loggerd.h b/selfdrive/loggerd/loggerd.h
index 59f4cb6709..ca5a638f85 100644
--- a/selfdrive/loggerd/loggerd.h
+++ b/selfdrive/loggerd/loggerd.h
@@ -115,4 +115,5 @@ struct LoggerdState {
   bool camera_synced[WideRoadCam + 1] = {};
 };
 
+bool sync_encoders(LoggerdState *state, CameraType cam_type, uint32_t frame_id);
 void loggerd_thread();
diff --git a/selfdrive/loggerd/tests/test_loggerd.cc b/selfdrive/loggerd/tests/test_loggerd.cc
new file mode 100644
index 0000000000..500aa6f338
--- /dev/null
+++ b/selfdrive/loggerd/tests/test_loggerd.cc
@@ -0,0 +1,50 @@
+#include <future>
+
+#include "catch2/catch.hpp"
+#include "selfdrive/loggerd/loggerd.h"
+
+int random_int(int min, int max) {
+  std::random_device dev;
+  std::mt19937 rng(dev());
+  std::uniform_int_distribution<std::mt19937::result_type> dist(min, max);
+  return dist(rng);
+}
+
+int get_synced_frame_id(LoggerdState *s, CameraType cam_type, int start_frame_id) {
+  int frame_id = start_frame_id;
+  while (!sync_encoders(s, cam_type, frame_id)) {
+    ++frame_id;
+    usleep(0);
+  }
+  return frame_id;
+};
+
+TEST_CASE("sync_encoders") {
+  const int max_waiting = GENERATE(1, 2, 3);
+
+  for (int test_cnt = 0; test_cnt < 10; ++test_cnt) {
+    LoggerdState s{.max_waiting = max_waiting};
+    std::vector<int> start_frames;
+    std::vector<std::future<int>> futures;
+
+    for (int i = 0; i < max_waiting; ++i) {
+      int start_frame_id = random_int(0, 20);
+      start_frames.push_back(start_frame_id);
+      futures.emplace_back(std::async(std::launch::async, get_synced_frame_id, &s, (CameraType)i, start_frame_id));
+    }
+
+    // get results
+    int synced_frame_id = 0;
+    for (int i = 0; i < max_waiting; ++i) {
+      if (i == 0) {
+        synced_frame_id = futures[i].get();
+        // require synced_frame_id equal start_frame_id if max_waiting == 1
+        if (max_waiting == 1) {
+          REQUIRE(synced_frame_id == start_frames[0]);
+        }
+      } else {
+        REQUIRE(futures[i].get() == synced_frame_id);
+      }
+    }
+  }
+}