test: add comprehensive test suite for visualization and comparison modules

tests/test_graph_view.py

@@ -0,0 +1,108 @@
+"""Tests for src/pygui/backend/visualization/graph_view.py."""
+import json
+from unittest.mock import MagicMock, PropertyMock, patch
+
+import pytest
+
+
+def _make_plot_widget():
+    """Create a mock PlotWidget with the interface GraphView expects."""
+    widget = MagicMock()
+    widget.removeItem = MagicMock()
+    widget.plot = MagicMock(return_value=MagicMock())
+    widget.setYRange = MagicMock()
+    widget.clear = MagicMock()
+    return widget
+
+
+class TestUpdateTrend:
+    def test_parses_valid_json(self):
+        from pygui.backend.visualization.graph_view import GraphView
+
+        gv = GraphView()
+        gv._plot_widget = _make_plot_widget()
+
+        gv.updateTrend(json.dumps([20.0, 25.0, 30.0]))
+
+        assert gv._plot_widget.plot.called
+        gv._plot_widget.setYRange.assert_called_once()
+
+    def test_rejects_invalid_json(self):
+        from pygui.backend.visualization.graph_view import GraphView
+
+        gv = GraphView()
+        gv._plot_widget = _make_plot_widget()
+
+        gv.updateTrend("not json")
+
+        assert not gv._plot_widget.plot.called
+
+    def test_rejects_none(self):
+        from pygui.backend.visualization.graph_view import GraphView
+
+        gv = GraphView()
+        gv._plot_widget = _make_plot_widget()
+
+        gv.updateTrend(None)
+
+        assert not gv._plot_widget.plot.called
+
+    def test_empty_list(self):
+        from pygui.backend.visualization.graph_view import GraphView
+
+        gv = GraphView()
+        gv._plot_widget = _make_plot_widget()
+
+        gv.updateTrend("[]")
+
+        # Empty list means nothing to plot, but clear IS called
+        assert gv._plot_widget.plot.called is False
+
+    def test_no_plot_widget(self):
+        from pygui.backend.visualization.graph_view import GraphView
+
+        gv = GraphView()
+        assert gv._plot_widget is None
+
+        # Should not crash
+        gv.updateTrend("[1, 2, 3]")
+
+
+class TestUpdateComparison:
+    def test_parses_valid_json(self):
+        from pygui.backend.visualization.graph_view import GraphView
+
+        gv = GraphView()
+        gv._plot_widget = _make_plot_widget()
+
+        a = [10.0, 20.0, 30.0]
+        b = [12.0, 22.0, 32.0]
+        path = [[0, 0], [1, 1], [2, 2]]
+
+        gv.updateComparison(json.dumps(a), json.dumps(b), json.dumps(path))
+
+        assert gv._plot_widget.clear.called
+        assert gv._plot_widget.plot.call_count == 2
+
+    def test_rejects_invalid_json(self):
+        """clear() is called before parsing, so it always fires on valid widget."""
+        from pygui.backend.visualization.graph_view import GraphView
+
+        gv = GraphView()
+        gv._plot_widget = _make_plot_widget()
+
+        gv.updateComparison("bad", json.dumps([1]), json.dumps([]))
+
+        # clear() is called before parsing — it always fires
+        assert gv._plot_widget.clear.called
+        # But plot() should NOT be called since parsing fails
+        assert not gv._plot_widget.plot.called
+
+    def test_no_plot_widget(self):
+        from pygui.backend.visualization.graph_view import GraphView
+
+        gv = GraphView()
+        assert gv._plot_widget is None
+
+        # Should not crash
+        gv.updateComparison("[1,2]", "[3,4]", "[[0,0]]")