diff --git a/api/src/backend/api/tests/test_validators.py b/api/src/backend/api/tests/test_validators.py
new file mode 100644
index 0000000000..f1a067112d
--- /dev/null
+++ b/api/src/backend/api/tests/test_validators.py
@@ -0,0 +1,35 @@
+import pytest
+from django.core.exceptions import ValidationError
+
+from api.validators import cron_5_fields_validator
+
+
+class TestCron5FieldsValidator:
+    @pytest.mark.parametrize(
+        "expression",
+        [
+            "* * * * *",
+            "*/30 * * * *",
+            "0 2 * * 1-5",
+            "15,45 8-18 * 1,6,12 1-5",
+        ],
+    )
+    def test_accepts_valid_expressions(self, expression):
+        cron_5_fields_validator(expression)
+
+    @pytest.mark.parametrize(
+        "expression",
+        [
+            "*/30 * * *",
+            "@daily",
+            "0 24 * * *",
+            "0 2 0 * *",
+            "0 2 * 13 *",
+            "0 2 * * 9",
+            "*/0 * * * *",
+            "",
+        ],
+    )
+    def test_rejects_invalid_expressions(self, expression):
+        with pytest.raises(ValidationError):
+            cron_5_fields_validator(expression)