test: add unit tests for rgb/hex color conversion helpers

tests/test_core/test_colors/test_color_conversions.py

@@ -0,0 +1,49 @@
+import pytest
+
+from _plotly_utils.colors import (
+    find_intermediate_color,
+    hex_to_rgb,
+    label_rgb,
+    unlabel_rgb,
+)
+
+
+def test_hex_to_rgb_basic_values():
+    assert hex_to_rgb("#ffffff") == (255, 255, 255)
+    assert hex_to_rgb("#000000") == (0, 0, 0)
+    assert hex_to_rgb("#aabbcc") == (170, 187, 204)
+
+
+def test_label_rgb_formats_tuple():
+    assert label_rgb((255, 0, 0)) == "rgb(255, 0, 0)"
+    assert label_rgb((1, 2, 3)) == "rgb(1, 2, 3)"
+
+
+def test_unlabel_rgb_parses_string():
+    assert unlabel_rgb("rgb(255, 0, 0)") == (255.0, 0.0, 0.0)
+    assert unlabel_rgb("rgb(1, 2, 3)") == (1.0, 2.0, 3.0)
+
+
+def test_label_and_unlabel_are_inverses():
+    assert unlabel_rgb(label_rgb((10, 20, 30))) == (10.0, 20.0, 30.0)
+
+
+def test_find_intermediate_color_tuple_midpoint():
+    assert find_intermediate_color((0, 0, 0), (1, 1, 1), 0.5) == (0.5, 0.5, 0.5)
+
+
+def test_find_intermediate_color_endpoints():
+    low, high = (0.0, 0.0, 0.0), (1.0, 1.0, 1.0)
+    assert find_intermediate_color(low, high, 0.0) == low
+    assert find_intermediate_color(low, high, 1.0) == high
+
+
+def test_find_intermediate_color_rgb_colortype():
+    result = find_intermediate_color(
+        "rgb(0, 0, 0)", "rgb(10, 20, 30)", 0.5, colortype="rgb"
+    )
+    assert result == "rgb(5.0, 10.0, 15.0)"
+
+
+if __name__ == "__main__":
+    raise SystemExit(pytest.main([__file__, "-v"]))