diff --git a/tests/test_iban.py b/tests/test_iban.py
index e3b0798..a15b2ba 100644
--- a/tests/test_iban.py
+++ b/tests/test_iban.py
@@ -17,3 +17,28 @@ def test_returns_true_on_valid_iban(value: str):
 def test_returns_failed_validation_on_invalid_iban(value: str):
     """Test returns failed validation on invalid iban."""
     assert isinstance(iban(value), ValidationError)
+
+
+@pytest.mark.parametrize("value", ["   ", "\t", "\n"])
+def test_returns_failed_validation_on_whitespace_only_iban(value: str):
+    """Test returns failed validation on whitespace-only iban."""
+    assert isinstance(iban(value), ValidationError)
+
+
+@pytest.mark.parametrize("value", ["gb82west12345698765432", "no9386011117947"])
+def test_returns_failed_validation_on_lowercase_iban(value: str):
+    """Test returns failed validation on lowercase iban (no normalization)."""
+    assert isinstance(iban(value), ValidationError)
+
+
+@pytest.mark.parametrize(
+    "value",
+    [
+        "XX82WEST12345698765432",
+        "ZZ9386011117947",
+        "QQ12345678901234567890123",
+    ],
+)
+def test_returns_failed_validation_on_invalid_country_code(value: str):
+    """Test returns failed validation on invalid country code prefix."""
+    assert isinstance(iban(value), ValidationError)