SIENTIAPDE-1579: Updated tests and refactored apply filters method

tests/sientia/test_models.py

@@ -9,9 +9,34 @@ from pytest import raises
 from model_manager.sientia.models import (
     DataPreprocessor,
     LinearRegressionModel,
+    _frontend_date_format_to_strftime,
 )
 
 
+class TestFrontendDateFormatToStrftime:
+    """Tests for _frontend_date_format_to_strftime (models module)."""
+
+    def test_none_or_empty_returns_none_or_empty(self):
+        """None or empty string returns None or falsy."""
+        assert _frontend_date_format_to_strftime(None) is None
+        assert _frontend_date_format_to_strftime('') is None
+
+    def test_dd_mm_yyyy_hh_mm_ss(self):
+        """Converts dd/MM/yyyy HH:mm:ss to strftime."""
+        result = _frontend_date_format_to_strftime('dd/MM/yyyy HH:mm:ss')
+        assert result == '%d/%m/%Y %H:%M:%S'
+
+    def test_yyyy_mm_dd(self):
+        """Converts yyyy-MM-dd to strftime."""
+        result = _frontend_date_format_to_strftime('yyyy-MM-dd')
+        assert result == '%Y-%m-%d'
+
+    def test_iso_datetime(self):
+        """Converts yyyy-MM-dd HH:mm:ss to strftime."""
+        result = _frontend_date_format_to_strftime('yyyy-MM-dd HH:mm:ss')
+        assert result == '%Y-%m-%d %H:%M:%S'
+
+
 class _IterableWithContains:
     def __init__(self, iterable, contains_values):
         self._iterable = iterable