Add DataFrame creation and filtering test

tests/preprocessing_test.py

@@ -1,9 +1,23 @@
 from app.constants import files
 from app.preprocessing import create_dataframe
-from pandas import DataFrame
+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():
-    for file in files.keys():
-        df = create_dataframe(file)
+    """
+    Verifes that the DataFrames are created and filtered properly
+    """
+    for dataset in DATASETS:
+        request_dataset(dataset)
+        df = create_dataframe(dataset)
+        remove(FILES[dataset])
         assert isinstance(df, DataFrame)