unittests: use setUpClass instead of setUp for class constant data

for test attributes that are class constant. This reduces the work that
must be done for each test case, allowing some of the setup work to be
done once for the entire class.

unittests/baseplatformtests.py

@@ -47,50 +47,53 @@ class BasePlatformTests(TestCase):
     prefix = '/usr'
     libdir = 'lib'
 
-    def setUp(self):
-        super().setUp()
-        self.maxDiff = None
+    @classmethod
+    def setUpClass(cls) -> None:
+        super().setUpClass()
+        cls.maxDiff = None
         src_root = str(PurePath(__file__).parents[1])
-        self.src_root = src_root
+        cls.src_root = src_root
         # Get the backend
-        self.backend_name = os.environ.get('MESON_UNIT_TEST_BACKEND', 'ninja')
-        backend_type = 'vs' if self.backend_name.startswith('vs') else self.backend_name
-        self.backend = getattr(Backend, backend_type)
-        self.meson_args = ['--backend=' + self.backend_name]
-        self.meson_native_files = []
-        self.meson_cross_files = []
-        self.meson_command = python_command + [get_meson_script()]
-        self.setup_command = self.meson_command + ['setup'] + self.meson_args
-        self.mconf_command = self.meson_command + ['configure']
-        self.mintro_command = self.meson_command + ['introspect']
-        self.wrap_command = self.meson_command + ['wrap']
-        self.rewrite_command = self.meson_command + ['rewrite']
+        cls.backend_name = os.environ.get('MESON_UNIT_TEST_BACKEND', 'ninja')
+        backend_type = 'vs' if cls.backend_name.startswith('vs') else cls.backend_name
+        cls.backend = getattr(Backend, backend_type)
+        cls.meson_args = ['--backend=' + cls.backend_name]
+        cls.meson_command = python_command + [get_meson_script()]
+        cls.setup_command = cls.meson_command + ['setup'] + cls.meson_args
+        cls.mconf_command = cls.meson_command + ['configure']
+        cls.mintro_command = cls.meson_command + ['introspect']
+        cls.wrap_command = cls.meson_command + ['wrap']
+        cls.rewrite_command = cls.meson_command + ['rewrite']
         # Backend-specific build commands
-        self.build_command, self.clean_command, self.test_command, self.install_command, \
-            self.uninstall_command = get_backend_commands(self.backend)
+        cls.build_command, cls.clean_command, cls.test_command, cls.install_command, \
+            cls.uninstall_command = get_backend_commands(cls.backend)
         # Test directories
-        self.common_test_dir = os.path.join(src_root, 'test cases/common')
-        self.python_test_dir = os.path.join(src_root, 'test cases/python')
-        self.rust_test_dir = os.path.join(src_root, 'test cases/rust')
-        self.vala_test_dir = os.path.join(src_root, 'test cases/vala')
-        self.framework_test_dir = os.path.join(src_root, 'test cases/frameworks')
-        self.unit_test_dir = os.path.join(src_root, 'test cases/unit')
-        self.rewrite_test_dir = os.path.join(src_root, 'test cases/rewrite')
-        self.linuxlike_test_dir = os.path.join(src_root, 'test cases/linuxlike')
-        self.objc_test_dir = os.path.join(src_root, 'test cases/objc')
-        self.objcpp_test_dir = os.path.join(src_root, 'test cases/objcpp')
-        self.darwin_test_dir = os.path.join(src_root, 'test cases/darwin')
+        cls.common_test_dir = os.path.join(src_root, 'test cases/common')
+        cls.python_test_dir = os.path.join(src_root, 'test cases/python')
+        cls.rust_test_dir = os.path.join(src_root, 'test cases/rust')
+        cls.vala_test_dir = os.path.join(src_root, 'test cases/vala')
+        cls.framework_test_dir = os.path.join(src_root, 'test cases/frameworks')
+        cls.unit_test_dir = os.path.join(src_root, 'test cases/unit')
+        cls.rewrite_test_dir = os.path.join(src_root, 'test cases/rewrite')
+        cls.linuxlike_test_dir = os.path.join(src_root, 'test cases/linuxlike')
+        cls.objc_test_dir = os.path.join(src_root, 'test cases/objc')
+        cls.objcpp_test_dir = os.path.join(src_root, 'test cases/objcpp')
+        cls.darwin_test_dir = os.path.join(src_root, 'test cases/darwin')
 
         # Misc stuff
-        if self.backend is Backend.ninja:
-            self.no_rebuild_stdout = ['ninja: no work to do.', 'samu: nothing to do']
+        if cls.backend is Backend.ninja:
+            cls.no_rebuild_stdout = ['ninja: no work to do.', 'samu: nothing to do']
         else:
             # VS doesn't have a stable output when no changes are done
             # XCode backend is untested with unit tests, help welcome!
-            self.no_rebuild_stdout = [f'UNKNOWN BACKEND {self.backend.name!r}']
+            cls.no_rebuild_stdout = [f'UNKNOWN BACKEND {cls.backend.name!r}']
         os.environ['COLUMNS'] = '80'
         os.environ['PYTHONIOENCODING'] = 'utf8'
 
+    def setUp(self):
+        super().setUp()
+        self.meson_native_files = []
+        self.meson_cross_files = []
         self.new_builddir()
 
     def change_builddir(self, newdir):