Add tests for checking the theme.

ci/configure_all.sh

@@ -1,7 +1,12 @@
 #!/usr/bin/env bash
 #
 # Run each configure for all supported frameworks, and store them in `dist/ci`.
-#
+# This requires the correct frameworks to be installed:
+#   - PyQt5
+#   - PyQt6
+#   - PySide6
+# And if using Python 3.10 or earlier:
+#   - PySide2
 
 set -eux pipefail
 

ci/theme.sh

@@ -0,0 +1,20 @@
+#!/usr/bin/env bash
+#
+# Use scripts to check if the theme determination works.
+
+set -eux pipefail
+
+ci_home="$(dirname "$(realpath "${BASH_SOURCE[0]}")")"
+project_home="$(dirname "${ci_home}")"
+cd "${project_home}/example"
+
+if [[ ! -v PYTHON ]]; then
+    PYTHON=python
+fi
+theme=$("${PYTHON}" -c "import breeze_theme; print(breeze_theme.get_theme())")
+if [[ "${theme}" != Theme.* ]]; then
+    >&2 echo "Unable to get the correct theme."
+    exit 1
+fi
+"${PYTHON}" -c "import breeze_theme; print(breeze_theme.is_light())"
+"${PYTHON}" -c "import breeze_theme; print(breeze_theme.is_dark())"