test: create a unit test skeleton

.pythonrc

@@ -1,12 +1,14 @@
 #!/usr/bin/env python3
 try:
+    # noinspection PyUnresolvedReferences
     import amazing_marvin
 except ModuleNotFoundError:
     import os
     import sys
 
     sys.path.insert(0, os.path.join(os.path.dirname(__file__), 'src'))
 
+    # noinspection PyUnresolvedReferences
     import amazing_marvin
 
 print(f"Type \"help({amazing_marvin.__name__})\" to learn about this package.")

tests/test_amazing_marvin.py

@@ -0,0 +1,53 @@
+import unittest
+from datetime import date
+
+# noinspection PyUnresolvedReferences
+from amazing_marvin import AmazingMarvinAPI, API_URL
+
+
+class MockResponse:
+    def __init__(self, content: str):
+        self.content = content
+
+    def raise_for_status(self) -> None:
+        pass
+
+
+class MockSession:
+    headers: dict = {}
+
+    def __init__(self, path_content: dict[str, str]) -> None:
+        self.path_content = path_content
+
+    def get(self, path: str) -> MockResponse:
+        return MockResponse(self.path_content[path])
+
+
+class MockRequestsModule:
+    def __init__(self, path_content: dict[str, str]) -> None:
+        self.path_content = path_content
+        self.Session = lambda: MockSession(self.path_content)
+
+
+class TestAmazingMarvinAPI(unittest.TestCase):
+
+    def setUp(self) -> None:
+        today = date.today()
+
+        self.api = AmazingMarvinAPI(
+            api_token='ignored_by_mock_requests_module',
+            requests_module=MockRequestsModule({
+                f'{API_URL}/me': '{}',
+                f'{API_URL}/todayItems?date={today.isoformat()}': '[]'
+            })
+        )
+
+    def test_me(self):
+        self.assertIsInstance(self.api.me(), dict)
+
+    def test_today_items(self):
+        self.assertIsInstance(self.api.today_items(), list)
+
+
+if __name__ == '__main__':
+    unittest.main()