Allow more signed integer types in test function arguments

Now that the C code supports the full range of intmax_t, allow any size of
signed integer type in the .data file parser.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/tests/scripts/test_generate_test_code.py b/tests/scripts/test_generate_test_code.py
index 7c0ac0c..effa46b 100755
--- a/tests/scripts/test_generate_test_code.py
+++ b/tests/scripts/test_generate_test_code.py
@@ -507,10 +507,10 @@
 
     def test_unsupported_arg(self):
         """
-        Test unsupported arguments (not among int, char * and data_t)
+        Test unsupported argument type
         :return:
         """
-        line = 'void entropy_threshold( char * a, data_t * h, char result )'
+        line = 'void entropy_threshold( char * a, data_t * h, unknown_t result )'
         self.assertRaises(ValueError, parse_function_arguments, line)
 
     def test_empty_params(self):