diff --git a/tests/transaction_tests.py b/tests/transaction_tests.py
index 62caa8a..1385d1c 100644
--- a/tests/transaction_tests.py
+++ b/tests/transaction_tests.py
@@ -3,6 +3,11 @@
 from transaction import Transaction
 
 
-def test_type():
-    t = Transaction(5)
-    assert_is_instance(t, Transaction, "correct type")
\ No newline at end of file
+def test_type(amount): 
+	t = Transaction(amount) 
+	assert_is_instance(t, Transaction, "correct type") 
+
+def test_type_call(): 
+	amounts = [5, 1000, -200, None]
+	for amount in amounts:
+		test_type(amount)