Add failing test case (invalid signature) for zero-length data

Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
diff --git a/tests/suites/test_suite_pkcs7.data b/tests/suites/test_suite_pkcs7.data
index 70233de..9948537 100644
--- a/tests/suites/test_suite_pkcs7.data
+++ b/tests/suites/test_suite_pkcs7.data
@@ -42,6 +42,10 @@
 depends_on:MBEDTLS_SHA1_C:MBEDTLS_SHA256_C
 pkcs7_verify:"data_files/pkcs7_zerolendata_detached.der":"data_files/pkcs7-rsa-sha256-1.der":"data_files/pkcs7_zerolendata.bin":0:0
 
+PKCS7 Signed Data Verification Fail zero-len data
+depends_on:MBEDTLS_SHA1_C:MBEDTLS_SHA256_C
+pkcs7_verify:"data_files/pkcs7_zerolendata_detached.der":"data_files/pkcs7-rsa-sha256-2.der":"data_files/pkcs7_zerolendata.bin":0:MBEDTLS_ERR_RSA_VERIFY_FAILED
+
 PKCS7 Signed Data Verification Pass SHA256 #9
 depends_on:MBEDTLS_SHA256_C
 pkcs7_verify:"data_files/pkcs7_data_cert_signed_sha256.der":"data_files/pkcs7-rsa-sha256-1.der":"data_files/pkcs7_data.bin":0:0