Add first unit test for heatpump COP calculation

tests/test_heatpump.py

@@ -0,0 +1,16 @@
+import pytest
+from modules.class_heatpump import Heatpump
+
+
+@pytest.fixture(scope='function')
+def heatpump() -> Heatpump:
+    """ Heatpump with 5 kw heating power and 24 h prediction
+    """
+    return Heatpump(5000, 24)
+
+class TestHeatpump:
+    def test_cop(self, heatpump):
+        """Testing calculate COP for variouse outside temperatures"""
+        assert heatpump.cop_berechnen(-10) == 2.0, "COP for -10 degree isn't correct"
+        assert heatpump.cop_berechnen(0) == 3.0, "COP for 0 degree isn't correct"
+        assert heatpump.cop_berechnen(10) == 4.0, "COP for 10 degree isn't correct"