Add tests for OID parsing from string

Signed-off-by: David Horstmann <david.horstmann@arm.com>
diff --git a/tests/suites/test_suite_oid.function b/tests/suites/test_suite_oid.function
index 3004b65..329bd8b 100644
--- a/tests/suites/test_suite_oid.function
+++ b/tests/suites/test_suite_oid.function
@@ -117,3 +117,29 @@
     }
 }
 /* END_CASE */
+
+/* BEGIN_CASE */
+void oid_from_numeric_string(char *oid_str, int error_ret,
+                             data_t *exp_oid_buf)
+{
+    mbedtls_asn1_buf oid = { 0, 0, NULL };
+    mbedtls_asn1_buf exp_oid = { 0, 0, NULL };
+    int ret;
+
+    exp_oid.tag = MBEDTLS_ASN1_OID;
+    exp_oid.p = exp_oid_buf->x;
+    exp_oid.len = exp_oid_buf->len;
+
+    ret = mbedtls_oid_from_numeric_string(&oid, oid_str, strlen(oid_str));
+
+    if (error_ret == 0) {
+        TEST_EQUAL(oid.len, exp_oid.len);
+        TEST_ASSERT(memcmp(oid.p, exp_oid.p, oid.len) == 0);
+        mbedtls_free(oid.p);
+        oid.p = NULL;
+        oid.len = 0;
+    } else {
+        TEST_EQUAL(ret, error_ret);
+    }
+}
+/* END_CASE */