diff --git a/tests/scripts/generate_test_keys.py b/tests/scripts/generate_test_keys.py
index 65e427983a..335e84890b 100755
--- a/tests/scripts/generate_test_keys.py
+++ b/tests/scripts/generate_test_keys.py
@@ -6,7 +6,7 @@
 """Module generating EC and RSA keys to be used in test_suite_pk instead of
 generating the required key at run time. This helps speeding up testing."""
 
-from typing import Iterator
+from typing import Iterator, List
 import re
 import argparse
 import scripts_path # pylint: disable=unused-import
@@ -89,8 +89,33 @@ def get_look_up_table_entry(key_type: str, group_id_or_keybits: str,
     yield "      {0}, sizeof({0}),\n".format(priv_array_name)
     yield "      {0}, sizeof({0}) }},".format(pub_array_name)
 
+
+def write_output_file(output_file_name: str, arrays: List[str], look_up_table: List[str]):
+    with open(output_file_name, 'wt') as output:
+        output.write("""
+/*********************************************************************************
+ * This file was automatically generated from tests/scripts/generate_test_keys.py.
+ * Please do not edit it manually.
+ *********************************************************************************/
+""")
+        output.write(''.join(arrays))
+        output.write("""
+struct predefined_key_element {{
+    int group_id;  // EC group ID; 0 for RSA keys
+    int keybits;  // bits size of RSA key; 0 for EC keys
+    const unsigned char *priv_key;
+    size_t priv_key_len;
+    const unsigned char *pub_key;
+    size_t pub_key_len;
+}};
+
+struct predefined_key_element predefined_keys[] = {{
+{}
+}};
+""".format("\n".join(look_up_table)))
+
+
 def main() -> None:
-    #pylint: disable=too-many-locals
     default_output_path = guess_project_root() + "/tests/src/test_keys.h"
 
     argparser = argparse.ArgumentParser()
@@ -98,14 +123,8 @@ def main() -> None:
     args = argparser.parse_args()
 
     output_file = args.output
-    output_file = open(output_file, 'wt')
-    output_file.write(
-        "/*********************************************************************************\n" +
-        " * This file was automatically generated from tests/scripts/generate_test_keys.py.\n" +
-        " * Please do not edit it manually.\n" +
-        " *********************************************************************************/\n"
-    )
 
+    arrays = []
     look_up_table = []
 
     # Get a list of private keys only in order to get a single item for every
@@ -139,7 +158,7 @@ def main() -> None:
             c_array_priv = convert_der_to_c(array_name_priv, ASYMMETRIC_KEY_DATA[priv_key][bits])
             c_array_pub = convert_der_to_c(array_name_pub, ASYMMETRIC_KEY_DATA[pub_key][bits])
             # Write the C array to the output file
-            output_file.write(''.join(["\n", c_array_priv, "\n", c_array_pub, "\n"]))
+            arrays.append(''.join(["\n", c_array_priv, "\n", c_array_pub, "\n"]))
             # Update the lookup table
             if key_type == "ec":
                 group_id_or_keybits = "MBEDTLS_ECP_DP_" + curve.upper()
@@ -147,22 +166,8 @@ def main() -> None:
                 group_id_or_keybits = str(bits)
             look_up_table.append(''.join(get_look_up_table_entry(key_type, group_id_or_keybits,
                                                                  array_name_priv, array_name_pub)))
-    # Write the lookup table: the struct containing pointers to all the arrays we created above.
-    output_file.write("""
-struct predefined_key_element {
-    int group_id;  // EC group ID; 0 for RSA keys
-    int keybits;  // bits size of RSA key; 0 for EC keys
-    const unsigned char *priv_key;
-    size_t priv_key_len;
-    const unsigned char *pub_key;
-    size_t pub_key_len;
-};
 
-struct predefined_key_element predefined_keys[] = {
-""")
-    output_file.write("\n".join(look_up_table))
-    output_file.write("\n};\n")
-    output_file.flush()
+    write_output_file(output_file, arrays, look_up_table)
 
 if __name__ == '__main__':
     main()