Add mock tests

tests/test_mock.py

@@ -0,0 +1,26 @@
+import json
+from pathlib import Path
+from unittest.mock import Mock, patch
+
+import sunblock
+
+
+# Mocking allows us to replace interfaces that require network
+# connectivity or external infrastructure with a interface that mimics
+# the return values, thus enabling testing of such code without having
+# to setup aforesaid infrastructure. Here we mimic the requests.get()
+# call to OpenMeteo.
+@patch("sunblock.requests")
+def test_fetch(mock_requests):
+    loc = sunblock.Location(51.76, -1.24)
+    with Path(__file__).with_name("openmeteo.json").open() as fp:
+        data = json.load(fp)
+        mock_requests.get.return_value = Mock(
+            **{
+                "status_code": 200,
+                "json.return_value": data,
+            }
+        )
+        res = sunblock.fetch(loc)
+        mock_requests.get.assert_called_once()
+        assert len(res["hourly"]["time"]) == 24 * 7  # hourly data for 7 days