fix

tests/test_processing.py

@@ -9,6 +9,7 @@ from rfg_adc_plotter.constants import FFT_LEN, SWEEP_FREQ_MAX_GHZ, SWEEP_FREQ_MI
 from rfg_adc_plotter.gui.pyqtgraph_backend import (
     apply_working_range,
     apply_working_range_to_aux_curves,
+    coalesce_packets_for_ui,
     compute_background_subtracted_bscan_levels,
     decimate_curve_for_display,
     resolve_visible_fft_curves,
@@ -228,6 +229,30 @@ class ProcessingTests(unittest.TestCase):
         self.assertAlmostEqual(float(decimated_y[0]), float(ys[0]), places=6)
         self.assertAlmostEqual(float(decimated_y[-1]), float(ys[-1]), places=6)
 
+    def test_coalesce_packets_for_ui_keeps_newest_packets(self):
+        packets = [
+            (np.asarray([float(idx)], dtype=np.float32), {"sweep": idx}, None)
+            for idx in range(6)
+        ]
+
+        kept, skipped = coalesce_packets_for_ui(packets, max_packets=2)
+
+        self.assertEqual(skipped, 4)
+        self.assertEqual(len(kept), 2)
+        self.assertEqual(int(kept[0][1]["sweep"]), 4)
+        self.assertEqual(int(kept[1][1]["sweep"]), 5)
+
+    def test_coalesce_packets_for_ui_never_returns_empty_for_non_empty_input(self):
+        packets = [
+            (np.asarray([1.0], dtype=np.float32), {"sweep": 1}, None),
+        ]
+
+        kept, skipped = coalesce_packets_for_ui(packets, max_packets=0)
+
+        self.assertEqual(skipped, 0)
+        self.assertEqual(len(kept), 1)
+        self.assertEqual(int(kept[0][1]["sweep"]), 1)
+
     def test_background_subtracted_bscan_levels_ignore_zero_floor(self):
         disp_fft_lin = np.zeros((4, 8), dtype=np.float32)
         disp_fft_lin[1, 2:6] = np.asarray([0.05, 0.1, 0.5, 2.0], dtype=np.float32)