inplement unit testing

tests.py

@@ -0,0 +1,29 @@
+import os
+import pandas as pd
+import pytest
+
+CSV_FILE = "data/fashion_magazines.csv"
+
+def test_file_exists():
+    assert os.path.exists(CSV_FILE) == True, "csv file does not exist"
+
+def test_columns_exist():
+    expected_columns = ['Customer','Amount Due']
+    try:
+        df = pd.read_csv(CSV_FILE)
+        for col in expected_columns:
+            assert col in df.columns
+    except Exception as e:
+        assert False, e
+
+@pytest.mark.parametrize("expected_customer,expected_amount",
+                        [["Bethann Schraub",102],
+                        ["Eryn Vilar",102],
+                        ["Janay Priolo",57],
+                        ["Lizabeth Letsche",237]])
+def test_values_exist(expected_customer, expected_amount):
+    try:
+        df = pd.read_csv(CSV_FILE)
+        assert df.loc[df['Customer'] == expected_customer]['Amount Due'].iloc[0] == expected_amount
+    except Exception as e:
+        assert False, e