Added Cocoa CSS keyword tests #8

Author: KlaraLindemalm

Diff for: changes/1814.misc.rst

@@ -1,2 +1 @@
-Support for CSS keywords in Windows.
-
+Support for CSS keywords in Windows & Cocoa.

Diff for: cocoa/tests_backend/fonts.py

@@ -1,3 +1,9 @@
+from travertino.constants import (
+    FONT_SIZE_SCALE,
+    RELATIVE_FONT_SIZE_SCALE,
+    RELATIVE_FONT_SIZES,
+)
+
 from toga.fonts import (
     BOLD,
     CURSIVE,
@@ -48,6 +54,16 @@ def assert_font_options(self, weight=NORMAL, style=NORMAL, variant=NORMAL):
     def assert_font_size(self, expected):
         if expected == SYSTEM_DEFAULT_FONT_SIZE:
             assert self.font.pointSize == 13
+        elif isinstance(expected, str):
+            base_size = 13
+            if expected in RELATIVE_FONT_SIZES:
+                parent_size = getattr(self, "_parent_size", base_size)
+                expected_size = parent_size * RELATIVE_FONT_SIZE_SCALE.get(
+                    expected, 1.0
+                )
+            else:
+                expected_size = base_size * FONT_SIZE_SCALE.get(expected, 1.0)
+            assert abs(self.font.pointSize - expected_size) < 0.01
         else:
             assert self.font.pointSize == expected * 96 / 72