diff --git a/Retos/Reto #26 - TESTING [Media]/python/nlarrea.py b/Retos/Reto #26 - TESTING [Media]/python/nlarrea.py
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+++ b/Retos/Reto #26 - TESTING [Media]/python/nlarrea.py	
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+"""
+ * Crea tres test sobre el reto 12: "Viernes 13".
+ * - Puedes copiar una solución ya creada por otro usuario en
+ *   el lenguaje que estés utilizando.
+ * - Debes emplear un mecanismo de ejecución de test que posea
+ *   el lenguaje de programación que hayas seleccionado.
+ * - Los tres test deben de funcionar y comprobar
+ *   diferentes situaciones (a tu elección).
+"""
+
+import unittest
+from datetime import datetime
+
+
+def is_friday_thirteen(month, year):
+    if not isinstance(month, int) or not isinstance(year, int):
+        assert TypeError("Invalid month or year. Use integer numbers.")
+
+    if month < 1 or month > 12:
+        return "Month is out of range."
+    
+    date = datetime(year, month, 13)
+    return date.weekday() == 4
+
+
+class TestReto12(unittest.TestCase):
+    def test_number_month(self):
+        is_friday_13th = is_friday_thirteen(1, 2023)
+        self.assertTrue(is_friday_13th)
+
+        is_friday_13th = is_friday_thirteen(3, 2022)
+        self.assertFalse(is_friday_13th)
+
+    def test_month_out_of_range(self):
+        is_friday_13th = is_friday_thirteen(14, 2023)
+        self.assertEqual(is_friday_13th, "Month is out of range.")
+        
+        is_friday_13th = is_friday_thirteen(-1, 2023)
+        self.assertEqual(is_friday_13th, "Month is out of range.")
+
+    def test_not_numeric_values(self):
+        with self.assertRaises(TypeError):
+            is_friday_thirteen("6", 1998)
+
+        with self.assertRaises(TypeError):
+            is_friday_thirteen(6, "1998")
+
+
+if __name__ == "__main__":
+    unittest.main()
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