add test

.gitignore

@@ -2,3 +2,4 @@
 /env
 build
 dist
+tests/__pycache__/test_class_demo.cpython-311-pytest-7.4.4.pyc

tests/test_class_demo.py

@@ -0,0 +1,9 @@
+class TestClassDemoInstance:
+    value = 0
+
+    def test_one(self):
+        self.value = 1
+        assert self.value == 1
+
+    def test_two(self):
+        assert self.value != 1