added unit test, updated Readme and picture

tests/test_slovak_datetime_formatter.py

@@ -0,0 +1,34 @@
+import unittest
+from datetime import datetime
+import csv
+import imp
+
+get_datetime_as_slovak_sentence = imp.load_source(
+    "slovak_datetime_formatter", "../lib/slovak_datetime_formatter.py"
+).get_datetime_as_slovak_sentence
+
+
+class TestSlovakDateTimeFormatter(unittest.TestCase):
+    def test(self):
+        test_data = []
+        with open("test_data.csv") as file:
+            reader = csv.reader(file, delimiter=";")
+            for row in reader:
+                if row:
+                    test_data.append(row)
+
+        for time_str, date_str, expected_text in test_data:
+            test_datetime = datetime(
+                int(date_str.split("-")[2]),
+                int(date_str.split("-")[1]),
+                int(date_str.split("-")[0]),
+                int(time_str.split(":")[0]),
+                int(time_str.split(":")[1]),
+            )
+
+            output_text = get_datetime_as_slovak_sentence(test_datetime)
+            self.assertEqual(output_text, expected_text)
+
+
+if __name__ == "__main__":
+    unittest.main()