A simple test infrastructure -- idea stolen from Gaurav.

src/platform/vboot_reference/cgptlib/cgpt.c

 /* Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "cgpt.h"
 
 /* stub code */
 static int start[] = { 34, 10034 };
 
 int GPTInit(GPTData_t *gpt) {
-        gpt->current_kernel = 1;
-        return 0;
+  gpt->current_kernel = 1;
+  return 0;
 }
 
 int GPTNextKernelEntry(GPTData_t *gpt, uint64_t *start_sector, uint64_t *size) {
-        gpt->current_kernel ^= 1;
-        if (start_sector) *start_sector = start[gpt->current_kernel];
-        if (size) *size = 10000;
-        return 0;
+  gpt->current_kernel ^= 1;
+  if (start_sector) *start_sector = start[gpt->current_kernel];
+  if (size) *size = 10000;
+  return 0;
 }
 
 int GPTUpdateKernelEntry(GPTData_t *gpt, uint32_t update_type) {
-        gpt->modified |= (GPT_MODIFIED_HEADER1 | GPT_MODIFIED_ENTRIES1) <<
-                         gpt->current_kernel;
-        return 0;
+  gpt->modified |= (GPT_MODIFIED_HEADER1 | GPT_MODIFIED_ENTRIES1) <<
+                   gpt->current_kernel;
+  return 0;
 }