Add DataFrame creation and filtering test

tests/preprocessing_test.py

@@ -7,18 +7,12 @@ from os import remove
 
 
 def test_dataset_request():
-    """
-    Checks that the datasets URLs are reachable
-    """
     for dataset in DATASETS:
         response = get(URL.format(dataset))
         assert response.status_code == 200
 
 
 def test_dataframe_creation():
-    """
-    Verifes that the DataFrames are created and filtered properly
-    """
     for dataset in DATASETS:
         request_dataset(dataset)
         df = create_dataframe(dataset)