Add mbedtls_ct_error_if, with tests

Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
diff --git a/tests/suites/test_suite_constant_time.function b/tests/suites/test_suite_constant_time.function
index 3d5fa7f..b9a78c8 100644
--- a/tests/suites/test_suite_constant_time.function
+++ b/tests/suites/test_suite_constant_time.function
@@ -115,6 +115,27 @@
 /* END_CASE */
 
 /* BEGIN_CASE */
+void mbedtls_ct_error_if(int cond, int t, int f)
+{
+    mbedtls_ct_condition_t c = mbedtls_ct_bool(cond);
+
+    mbedtls_ct_uint_t expected = c ? t : f;
+    mbedtls_ct_uint_t expected0 = c ? t : 0;
+
+    TEST_CF_SECRET(&c, sizeof(c));
+    TEST_CF_SECRET(&t, sizeof(t));
+    TEST_CF_SECRET(&f, sizeof(f));
+
+    TEST_EQUAL(mbedtls_ct_error_if(c, t, f), expected);
+    TEST_EQUAL(mbedtls_ct_error_if_else_0(c, t), expected0);
+
+    TEST_CF_PUBLIC(&c, sizeof(c));
+    TEST_CF_PUBLIC(&t, sizeof(t));
+    TEST_CF_PUBLIC(&f, sizeof(f));
+}
+/* END_CASE */
+
+/* BEGIN_CASE */
 void mbedtls_ct_if(char *c_str, char *t_str, char *f_str)
 {
     mbedtls_ct_condition_t c = mbedtls_ct_bool(strtoull(c_str, NULL, 16));