Simplify test setup using a helper to convert hex strings to byte arrays

test/hex_helper.h

@@ -0,0 +1,29 @@
+#ifndef HEX_HELPER_H
+#define HEX_HELPER_H
+
+#include <cstring>  // for strlen
+
+uint8_t* hex_string_to_array(const char* str) {
+  size_t len = strlen(str);
+  if (len % 2 != 0) {
+    // Cannot handle odd string length
+    return nullptr;
+  }
+  size_t data_len = len / 2;
+
+  uint8_t* data = new uint8_t[data_len];
+
+  // Convert each hexadecimal character pair to a byte
+  for (size_t i = 0; i < data_len; ++i) {
+    uint8_t high_nibble = str[i * 2] >= 'A' ? (str[i * 2] - 'A' + 10) : (str[i * 2] - '0');
+    uint8_t low_nibble = str[i * 2 + 1] >= 'A' ? (str[i * 2 + 1] - 'A' + 10) : (str[i * 2 + 1] - '0');
+    
+    // Combine the nibbles into a byte
+    data[i] = (high_nibble << 4) | low_nibble;
+  }
+
+  // Return the pointer to the allocated data array
+  return data;
+}
+
+#endif // HEX_HELPER_H