Rename test to tests; fix equator length.

tests/test_color.py

@@ -0,0 +1,26 @@
+"""
+Test color functions.
+"""
+from colour import Color
+
+from roentgen.color import get_gradient_color, is_bright
+from roentgen.util import MinMax
+
+__author__ = "Sergey Vartanov"
+__email__ = "me@enzet.ru"
+
+
+def test_is_bright() -> None:
+    """Test detecting color brightness."""
+    assert is_bright(Color("white"))
+    assert is_bright(Color("yellow"))
+    assert not is_bright(Color("brown"))
+    assert not is_bright(Color("black"))
+
+
+def test_gradient() -> None:
+    """Test color picking from gradient."""
+    color: Color = get_gradient_color(
+        0.5, MinMax(0, 1), [Color("black"), Color("white")]
+    )
+    assert color == Color("#7F7F7F")