Add DataFrame creation and filtering test

tests/preprocessing_test.py

@@ -1,7 +1,4 @@
-from pandas import DataFrame
-from requests import get
-from app.constants import URL, COLUMNS, FILES, DATASETS
-from app.request_datasets import request_dataset
+from app.constants import files
 from app.preprocessing import create_dataframe
 from os import remove
 
@@ -24,4 +21,3 @@ def test_dataframe_creation():
         df = create_dataframe(dataset)
         remove(FILES[dataset])
         assert isinstance(df, DataFrame)
-        assert list(df) == COLUMNS[dataset]