Refactor code structure for improved readability and maintainability

tests/test_session_model.py

@@ -0,0 +1,28 @@
+from pygui.backend.frame import Frame
+from pygui.backend.threshold_classifier import ThresholdConfig, BAND_HIGH, BAND_IN, BAND_LOW
+from pygui.backend.session_model import SessionModel, SessionUpdate
+
+
+
+def test_manual_banding_and_stats():
+    model = SessionModel(ThresholdConfig(set_point=149.0, margin=1.0, auto=False))
+    update = model.process(Frame(seq=7, time=1.0, values=[151.0, 149.0, 147.0]))
+    assert update.seq == 7
+    assert update.bands == [BAND_HIGH, BAND_IN, BAND_LOW]
+    assert update.stats.avg == 149.0
+    assert (update.target, update.margin) == (149.0, 1.0)
+    assert update.state in ("idle", "ramp", "set")
+    
+def test_auto_banding_uses_mean_and_sigma():
+    model = SessionModel(ThresholdConfig(auto=True))
+    # Tight cluster around 149 -> small σ -> the 200.0 outlier reads HIGH
+    update = model.process(Frame(seq=0, time=0.0, values=[149.0, 149.0, 149.0, 200.0]))
+    assert update.bands[3] == BAND_HIGH
+    assert update.target == update.stats.avg
+    
+def test_set_thresholds_reband_on_next_frame():
+    m = SessionModel(ThresholdConfig(set_point=149.0, margin=1.0, auto=False))
+    m.set_thresholds(ThresholdConfig(set_point=149.0, margin=5.0, auto=False))
+    upd = m.process(Frame(seq=0, time=0.0, values=[151.0]))
+    assert upd.bands == [BAND_IN]
+