diff --git a/validators/test_validators.py b/validators/test_validators.py
index b959892..16d3a9a 100644
--- a/validators/test_validators.py
+++ b/validators/test_validators.py
@@ -6,9 +6,11 @@ def test_mandatory():
     assert mandatory("Foo Bar") == True
     assert mandatory("1970-01-01") == True
     assert mandatory("") == False
+    assert mandatory(None) == False
 
 
 def test_empty():
+    assert empty(None) == True
     assert empty("") == True
     assert empty(" ") == False
     assert empty("Foo") == False
@@ -22,12 +24,18 @@ def test_iso_date():
     assert iso_date("1970/01/01") == False
     assert iso_date("1.1.1970") == False
     assert iso_date("01.01.1970") == False
+    assert iso_date("") == False
+    assert iso_date(None) == False
 
 
 def test_valid_iban():
     assert valid_iban("DE89 3704 0044 0532 0130 00") == True
+    assert valid_iban("DE89370400440532013000") == True
     assert valid_iban("DX89 3704 0044 0532 0130 00") == False
     assert valid_iban("DE99 3704 0044 0532 0130 00") == False
+    assert valid_iban("") == False
+    assert valid_iban(None) == False
+    assert valid_iban("DE89 3704 0044 0532 0130 00".split()) == False
 
 
 def test_valid_bic():
@@ -35,3 +43,8 @@ def test_valid_bic():
     assert valid_bic("PBNKDXFFXXX") == False
     assert valid_bic("PBNKDXFFXXXX") == False
     assert valid_bic("PBN1DXFFXXX") == False
+    assert valid_bic("") == False
+    assert valid_bic(None) == False
+    assert valid_bic("PBNKDEFFXXX".split()) == False
+
+