tests: Test that brand-backed themes compile without error

Author: gadenbuie

tests/pytest/test_theme.py

@@ -257,3 +257,33 @@ def test_theme_add_sass_layer_file():
     assert theme._defaults == ["// defaults 1\n// defaults 2\n"]
     assert theme._mixins == ["// mixins\n"]
     assert theme._rules == ["// rules 1\n// rules 2\n"]
+
+@skip_on_windows
+@pytest.mark.parametrize("preset", shiny_theme_presets)
+def test_theme_from_brand_base_case_compiles(preset: str):
+    brand_txt = f"""
+meta:
+  name: Brand Test
+defaults:
+  shiny:
+    theme:
+      preset: {preset}
+    """
+
+    with tempfile.TemporaryDirectory() as tmpdir:
+        with open(f"{tmpdir}/_brand.yml", "w") as f:
+            f.write(brand_txt)
+
+        theme = Theme.from_brand(f"{tmpdir}")
+
+        # Check that the theme preset is set from the brand
+        assert theme.preset == preset
+
+        # Check that the brand Sass layer is included
+        assert any(["brand-choose" in f for f in theme._functions])
+        assert any(["brand: initial" in d for d in theme._defaults])
+        assert any(["brand: brand rules" in r for r in theme._rules])
+
+        # Check that the CSS compiles without error
+        css = theme.to_css()
+        assert isinstance(css, str)