diff --git a/tests/ctypesgentest.py b/tests/ctypesgentest.py
index e44eee3a..36ad3e26 100644
--- a/tests/ctypesgentest.py
+++ b/tests/ctypesgentest.py
@@ -32,22 +32,19 @@ def module_from_code(name, python_code):
 
 def generate(header_str, args=[], lang="py"):
     
-    tmp_header = tempfile.NamedTemporaryFile()
-    tmp_header.write(header_str.encode())
-    tmp_header.seek(0)
-    tmp_out = tempfile.NamedTemporaryFile()
-    ctypesgen_main(["-i", tmp_header.name, "-o", tmp_out.name, "--output-language", lang, *args])
+    tmp_in = TEST_DIR/"tmp_in.h"
+    tmp_in.write_text(header_str)
+    tmp_out = TEST_DIR/"tmp_out.h"
+    ctypesgen_main(["-i", tmp_in, "-o", tmp_out, "--output-language", lang, *args])
+    content = tmp_out.read_text()
     
-    tmp_header_name = tmp_header.name
-    tmp_header.close()
-    tmp_out.seek(0)
-    content = tmp_out.read().decode()
-    tmp_out.close()
+    tmp_in.unlink()
+    tmp_out.unlink()
     
     if lang.startswith("py"):
         return module_from_code("tmp_module", content)
     elif lang == "json":
-        return json.loads(content), tmp_header_name
+        return json.loads(content), str(tmp_in)
     else:
         assert False
 
diff --git a/tests/testsuite.py b/tests/testsuite.py
index b1d3309d..a82a7c17 100755
--- a/tests/testsuite.py
+++ b/tests/testsuite.py
@@ -2550,7 +2550,7 @@ class MacromanEncodeTest(unittest.TestCase):
 
     @classmethod
     def setUpClass(cls):
-        cls.mac_roman_file = "temp_mac.h"
+        cls.mac_roman_file = TEST_DIR/"temp_mac.h"
         mac_header_str = b"""
         #define kICHelper                       "\xa9\\pHelper\xa5"
 
@@ -2559,8 +2559,8 @@ def setUpClass(cls):
         with open(cls.mac_roman_file, "wb") as mac_file:
             mac_file.write(mac_header_str)
 
-        header_str = """
-        #include "temp_mac.h"
+        header_str = f"""
+        #include "{cls.mac_roman_file}"
 
         #define MYSTRING kICHelper