diff --git a/tests/suites/test_suite_pkwrite.data b/tests/suites/test_suite_pkwrite.data
index f0a8d7f..25767ff 100644
--- a/tests/suites/test_suite_pkwrite.data
+++ b/tests/suites/test_suite_pkwrite.data
@@ -1,95 +1,95 @@
 Public key write check RSA
 depends_on:MBEDTLS_RSA_C:MBEDTLS_BASE64_C
-pk_write_pubkey_check:"data_files/server1.pubkey":0
+pk_write_pubkey_check:"data_files/server1.pubkey":TEST_PEM
 
 Public key write check RSA (DER)
 depends_on:MBEDTLS_RSA_C:MBEDTLS_BASE64_C
-pk_write_pubkey_check:"data_files/server1.pubkey.der":1
+pk_write_pubkey_check:"data_files/server1.pubkey.der":TEST_DER
 
 Public key write check RSA 4096
 depends_on:MBEDTLS_RSA_C:MBEDTLS_BASE64_C
-pk_write_pubkey_check:"data_files/rsa4096_pub.pem":0
+pk_write_pubkey_check:"data_files/rsa4096_pub.pem":TEST_PEM
 
 Public key write check RSA 4096 (DER)
 depends_on:MBEDTLS_RSA_C:MBEDTLS_BASE64_C
-pk_write_pubkey_check:"data_files/rsa4096_pub.pem.der":1
+pk_write_pubkey_check:"data_files/rsa4096_pub.pem.der":TEST_DER
 
 Public key write check EC 192 bits
 depends_on:MBEDTLS_ECP_LIGHT:MBEDTLS_BASE64_C:MBEDTLS_ECP_DP_SECP192R1_ENABLED
-pk_write_pubkey_check:"data_files/ec_pub.pem":0
+pk_write_pubkey_check:"data_files/ec_pub.pem":TEST_PEM
 
 Public key write check EC 192 bits (DER)
 depends_on:MBEDTLS_ECP_LIGHT:MBEDTLS_BASE64_C:MBEDTLS_ECP_DP_SECP192R1_ENABLED
-pk_write_pubkey_check:"data_files/ec_pub.pem.der":1
+pk_write_pubkey_check:"data_files/ec_pub.pem.der":TEST_DER
 
 Public key write check EC 521 bits
 depends_on:MBEDTLS_ECP_LIGHT:MBEDTLS_BASE64_C:MBEDTLS_ECP_DP_SECP521R1_ENABLED
-pk_write_pubkey_check:"data_files/ec_521_pub.pem":0
+pk_write_pubkey_check:"data_files/ec_521_pub.pem":TEST_PEM
 
 Public key write check EC 521 bits (DER)
 depends_on:MBEDTLS_ECP_LIGHT:MBEDTLS_BASE64_C:MBEDTLS_ECP_DP_SECP521R1_ENABLED
-pk_write_pubkey_check:"data_files/ec_521_pub.pem.der":1
+pk_write_pubkey_check:"data_files/ec_521_pub.pem.der":TEST_DER
 
 Public key write check EC Brainpool 512 bits
 depends_on:MBEDTLS_ECP_LIGHT:MBEDTLS_BASE64_C:MBEDTLS_ECP_DP_BP512R1_ENABLED
-pk_write_pubkey_check:"data_files/ec_bp512_pub.pem":0
+pk_write_pubkey_check:"data_files/ec_bp512_pub.pem":TEST_PEM
 
 Public key write check EC Brainpool 512 bits (DER)
 depends_on:MBEDTLS_ECP_LIGHT:MBEDTLS_BASE64_C:MBEDTLS_ECP_DP_BP512R1_ENABLED
-pk_write_pubkey_check:"data_files/ec_bp512_pub.pem.der":1
+pk_write_pubkey_check:"data_files/ec_bp512_pub.pem.der":TEST_DER
 
 Private key write check RSA
 depends_on:MBEDTLS_RSA_C:MBEDTLS_BASE64_C
-pk_write_key_check:"data_files/server1.key":0
+pk_write_key_check:"data_files/server1.key":TEST_PEM
 
 Private key write check RSA (DER)
 depends_on:MBEDTLS_RSA_C:MBEDTLS_BASE64_C
-pk_write_key_check:"data_files/server1.key.der":1
+pk_write_key_check:"data_files/server1.key.der":TEST_DER
 
 Private key write check RSA 4096
 depends_on:MBEDTLS_RSA_C:MBEDTLS_BASE64_C
-pk_write_key_check:"data_files/rsa4096_prv.pem":0
+pk_write_key_check:"data_files/rsa4096_prv.pem":TEST_PEM
 
 Private key write check RSA 4096 (DER)
 depends_on:MBEDTLS_RSA_C:MBEDTLS_BASE64_C
-pk_write_key_check:"data_files/rsa4096_prv.pem.der":1
+pk_write_key_check:"data_files/rsa4096_prv.pem.der":TEST_DER
 
 Private key write check EC 192 bits
 depends_on:MBEDTLS_ECP_LIGHT:MBEDTLS_BASE64_C:MBEDTLS_ECP_DP_SECP192R1_ENABLED
-pk_write_key_check:"data_files/ec_prv.sec1.pem":0
+pk_write_key_check:"data_files/ec_prv.sec1.pem":TEST_PEM
 
 Private key write check EC 192 bits (DER)
 depends_on:MBEDTLS_ECP_LIGHT:MBEDTLS_BASE64_C:MBEDTLS_ECP_DP_SECP192R1_ENABLED
-pk_write_key_check:"data_files/ec_prv.sec1.pem.der":1
+pk_write_key_check:"data_files/ec_prv.sec1.pem.der":TEST_DER
 
 Private key write check EC 256 bits (top bit set)
 depends_on:MBEDTLS_ECP_LIGHT:MBEDTLS_BASE64_C:MBEDTLS_ECP_DP_SECP256R1_ENABLED
-pk_write_key_check:"data_files/ec_256_long_prv.pem":0
+pk_write_key_check:"data_files/ec_256_long_prv.pem":TEST_PEM
 
 Private key write check EC 256 bits (top bit set) (DER)
 depends_on:MBEDTLS_ECP_LIGHT:MBEDTLS_BASE64_C:MBEDTLS_ECP_DP_SECP256R1_ENABLED
-pk_write_key_check:"data_files/ec_256_long_prv.pem.der":1
+pk_write_key_check:"data_files/ec_256_long_prv.pem.der":TEST_DER
 
 Private key write check EC 521 bits
 depends_on:MBEDTLS_ECP_LIGHT:MBEDTLS_BASE64_C:MBEDTLS_ECP_DP_SECP521R1_ENABLED
-pk_write_key_check:"data_files/ec_521_prv.pem":0
+pk_write_key_check:"data_files/ec_521_prv.pem":TEST_PEM
 
 Private key write check EC 521 bits (DER)
 depends_on:MBEDTLS_ECP_LIGHT:MBEDTLS_BASE64_C:MBEDTLS_ECP_DP_SECP521R1_ENABLED
-pk_write_key_check:"data_files/ec_521_prv.pem.der":1
+pk_write_key_check:"data_files/ec_521_prv.pem.der":TEST_DER
 
 Private key write check EC 521 bits (top byte is 0)
 depends_on:MBEDTLS_ECP_LIGHT:MBEDTLS_BASE64_C:MBEDTLS_ECP_DP_SECP521R1_ENABLED
-pk_write_key_check:"data_files/ec_521_short_prv.pem":0
+pk_write_key_check:"data_files/ec_521_short_prv.pem":TEST_PEM
 
 Private key write check EC 521 bits (top byte is 0) (DER)
 depends_on:MBEDTLS_ECP_LIGHT:MBEDTLS_BASE64_C:MBEDTLS_ECP_DP_SECP521R1_ENABLED
-pk_write_key_check:"data_files/ec_521_short_prv.pem.der":1
+pk_write_key_check:"data_files/ec_521_short_prv.pem.der":TEST_DER
 
 Private key write check EC Brainpool 512 bits
 depends_on:MBEDTLS_ECP_LIGHT:MBEDTLS_BASE64_C:MBEDTLS_ECP_DP_BP512R1_ENABLED
-pk_write_key_check:"data_files/ec_bp512_prv.pem":0
+pk_write_key_check:"data_files/ec_bp512_prv.pem":TEST_PEM
 
 Private key write check EC Brainpool 512 bits (DER)
 depends_on:MBEDTLS_ECP_LIGHT:MBEDTLS_BASE64_C:MBEDTLS_ECP_DP_BP512R1_ENABLED
-pk_write_key_check:"data_files/ec_bp512_prv.pem.der":1
+pk_write_key_check:"data_files/ec_bp512_prv.pem.der":TEST_DER
diff --git a/tests/suites/test_suite_pkwrite.function b/tests/suites/test_suite_pkwrite.function
index 716ba44..a304e07 100644
--- a/tests/suites/test_suite_pkwrite.function
+++ b/tests/suites/test_suite_pkwrite.function
@@ -3,6 +3,11 @@
 #include "mbedtls/pem.h"
 #include "mbedtls/oid.h"
 
+typedef enum {
+    TEST_PEM,
+    TEST_DER
+} pkwrite_file_format_t;
+
 static void pk_write_check_common(char *key_file, int is_public_key, int is_der)
 {
     mbedtls_pk_context key;