diff --git a/cgptlib/tests/Makefile b/cgptlib/tests/Makefile
new file mode 100644
index 0000000..60871fa
--- /dev/null
+++ b/cgptlib/tests/Makefile
@@ -0,0 +1,20 @@
+# 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.
+
+CC ?= cc
+CFLAGS ?= -Wall -DNDEBUG -Werror -ansi
+LIBS = ../cgpt.a ../../common/libcommon.a
+OBJS = cgpt_test.o
+OUT = cgpt_test
+
+all: $(OUT)
+
+$(OUT): $(OBJS) $(LIBS)
+	$(CC) -o $@ $^
+
+.c.o:
+	$(CC) $(CFLAGS) $(INCLUDES) -c $< -o $@
+
+clean:
+	rm -rf $(OUT) $(OBJS)
diff --git a/cgptlib/tests/cgpt_test.c b/cgptlib/tests/cgpt_test.c
index b5b26e7..a451838 100644
--- a/cgptlib/tests/cgpt_test.c
+++ b/cgptlib/tests/cgpt_test.c
@@ -3,12 +3,219 @@
  * found in the LICENSE file.
  */
 
-#include "cgpt.h"
 #include "cgpt_test.h"
+#include <string.h>
+#include "cgpt.h"
+#include "gpt.h"
+#include "utility.h"
+
+/* Testing partition layout (sector_bytes=512)
+ *
+ *     LBA   Size  Usage
+ *       0      1  PMBR
+ *       1      1  primary partition header
+ *       2     32  primary partition entries (128B * 128)
+ *      34    100  kernel A
+ *     134    100  kernel B
+ *     234    100  root A
+ *     334    100  root B
+ *     434     32  secondary partition entries
+ *     466      1  secondary partition header
+ *     467
+ */
+#define DEFAULT_SECTOR_SIZE 512
+#define MAX_SECTOR_SIZE 4096
+#define DEFAULT_DRIVE_SECTORS 467
+#define PARTITION_ENTRIES_SIZE (16*1024)
 
 #define TEST_CASE(func) #func, func
 typedef int (*test_func)(void);
 
+/* NOT A REAL CRC32, it is fake before I call real one . FIXME */
+uint32_t CalculateCrc32(const uint8_t *start, size_t len) {
+  uint32_t buf = 0;
+  int i;
+  for (i = 0; i < len; i += 4, len -= 4) {
+    buf ^= *(uint32_t*)&start[i];
+  }
+  if (len >= 3) buf ^= start[i-2] << 16;
+  if (len >= 2) buf ^= start[i-3] << 8;
+  if (len >= 1) buf ^= start[i-4];
+  return buf;
+}
+
+/* Given a GptData pointer, first re-calculate entries CRC32 value,
+ * then reset header CRC32 value to 0, and calculate header CRC32 value.
+ * Both primary and secondary are updated. */
+void RefreshCrc32(struct GptData *gpt) {
+  GptHeader *header, *header2;
+  GptEntry *entries, *entries2;
+
+  header = (GptHeader*)gpt->primary_header;
+  entries = (GptEntry*)gpt->primary_entries;
+  header2 = (GptHeader*)gpt->secondary_header;
+  entries2 = (GptEntry*)gpt->secondary_entries;
+
+  header->entries_crc32 = CalculateCrc32((uint8_t*)entries,
+                                         sizeof(GptEntry));
+  header->header_crc32 = 0;
+  header->header_crc32 = CalculateCrc32((uint8_t*)header,
+                                        header->size);
+  header2->entries_crc32 = CalculateCrc32((uint8_t*)entries2,
+                                          sizeof(GptEntry));
+  header2->header_crc32 = 0;
+  header2->header_crc32 = CalculateCrc32((uint8_t*)header2,
+                                         header2->size);
+}
+
+/* Returns a pointer to a static GptData instance (no free is required).
+ * All fields are zero except 4 pointers linking to header and entries.
+ * All content of headers and entries are zero. */
+struct GptData* GetAClearGptData() {
+  static GptData_t gpt;
+  static uint8_t primary_header[MAX_SECTOR_SIZE];
+  static uint8_t primary_entries[PARTITION_ENTRIES_SIZE];
+  static uint8_t secondary_header[MAX_SECTOR_SIZE];
+  static uint8_t secondary_entries[PARTITION_ENTRIES_SIZE];
+
+  Memset(&gpt, 0, sizeof(gpt));
+  Memset(&primary_header, 0, sizeof(primary_header));
+  Memset(&primary_entries, 0, sizeof(primary_entries));
+  Memset(&secondary_header, 0, sizeof(secondary_header));
+  Memset(&secondary_entries, 0, sizeof(secondary_entries));
+
+  gpt.primary_header = primary_header;
+  gpt.primary_entries = primary_entries;
+  gpt.secondary_header = secondary_header;
+  gpt.secondary_entries = secondary_entries;
+
+  return &gpt;
+}
+
+/* Fills in most of fields and creates the layout described in the top of this
+ * file. */
+struct GptData*
+BuildTestGptData(uint32_t sector_bytes) {
+  GptData_t *gpt;
+  GptHeader *header, *header2;
+  GptEntry *entries, *entries2;
+  Guid chromeos_kernel = GPT_ENT_TYPE_CHROMEOS_KERNEL;
+
+  gpt = GetAClearGptData();
+  gpt->sector_bytes = sector_bytes;
+  gpt->drive_sectors = DEFAULT_DRIVE_SECTORS;
+
+  /* build primary */
+  header = (GptHeader*)gpt->primary_header;
+  entries = (GptEntry*)gpt->primary_entries;
+  Memcpy(header->signature, GPT_HEADER_SIGNATURE, sizeof(GPT_HEADER_SIGNATURE));
+  header->revision = GPT_HEADER_REVISION;
+  header->size = sizeof(GptHeader) - sizeof(header->padding);
+  header->my_lba = 1;
+  header->first_usable_lba = 34;
+  header->last_usable_lba = DEFAULT_DRIVE_SECTORS - 1 - 32 - 1;  /* 433 */
+  header->entries_lba = 2;
+  header->number_of_entries = 128;  /* 512B / 128B * 32sectors = 128 entries */
+  header->size_of_entry = 128;  /* bytes */
+  Memcpy(&entries[0].type, &chromeos_kernel, sizeof(chromeos_kernel));
+  entries[0].starting_lba = 34;
+  entries[0].ending_lba = 133;
+  Memcpy(&entries[1].type, &chromeos_kernel, sizeof(chromeos_kernel));
+  entries[1].starting_lba = 134;
+  entries[1].ending_lba = 233;
+  Memcpy(&entries[2].type, &chromeos_kernel, sizeof(chromeos_kernel));
+  entries[2].starting_lba = 234;
+  entries[2].ending_lba = 333;
+  Memcpy(&entries[3].type, &chromeos_kernel, sizeof(chromeos_kernel));
+  entries[3].starting_lba = 334;
+  entries[3].ending_lba = 433;
+
+  /* build secondary */
+  header2 = (GptHeader*)gpt->secondary_header;
+  entries2 = (GptEntry*)gpt->secondary_entries;
+  Memcpy(header2, header, sizeof(header));
+  Memcpy(entries2, entries, sizeof(entries));
+  header2->my_lba = DEFAULT_DRIVE_SECTORS - 1;  /* 466 */
+  header2->entries_lba = DEFAULT_DRIVE_SECTORS - 1 - 32;  /* 434 */
+
+  RefreshCrc32(gpt);
+  return gpt;
+}
+
+/* Dumps memory starting from [vp] with [len] bytes.
+ * Prints [memo] if not NULL. Example output:
+ *
+ *  00 01 02 03 04 05 06 07 - 08 09 0a 0b 0c 0d 0e 0f
+ *  10 11 12 13 14 15 16 17 - 18 19 1a 1b 1c 1d 1e 1f
+ *  ...
+ */
+static void dump(void *vp, int len, char* memo) {
+  uint8_t *start = vp;
+  int i;
+  if (memo) printf("--[%s]----------\n", memo);
+  for (i = 0; i < len; ++i) {
+    printf("%02x%s", start[i],
+                     (!(~i & 15) ? "\n" :
+                      !(~i & 7) ? " - ": " "));
+  }
+  if (i&15) printf("\n");
+}
+
+/* More formatted dump with GptData. */
+void DumpGptData(struct GptData *gpt) {
+  printf("DumpGptData(%p)...\n", gpt);
+  dump(gpt, sizeof(gpt), NULL);
+  dump(gpt->primary_header, sizeof(GptHeader), "Primary header");
+  dump(gpt->primary_entries, sizeof(GptEntry) * 8, "Primary entries");
+  dump(gpt->secondary_header, sizeof(GptHeader), "Secondary header");
+  dump(gpt->secondary_entries, sizeof(GptEntry) * 8,
+       "Secondary entries");
+}
+
+/* Tests if signature ("EFI PART") is checked. */
+int SignatureTest() {
+  int i;
+  GptData_t *gpt;
+  GptHeader *primary_header, *secondary_header;
+
+  gpt = BuildTestGptData(DEFAULT_SECTOR_SIZE);
+  primary_header = (GptHeader*)gpt->primary_header;
+  secondary_header = (GptHeader*)gpt->secondary_header;
+
+  EXPECT(GPT_SUCCESS == GptInit(gpt));
+
+  /* change every char in signature of primary. Secondary is still valid. */
+  for (i = 0; i < 8; ++i) {
+    gpt->primary_header[i] ^= 0xff;
+    RefreshCrc32(gpt);
+    EXPECT(GPT_SUCCESS == GptInit(gpt));
+    gpt->primary_header[i] ^= 0xff;
+    RefreshCrc32(gpt);
+  }
+
+  /* change every char in signature of secondary. Primary is still valid. */
+  for (i = 0; i < 8; ++i) {
+    gpt->secondary_header[i] ^= 0xff;
+    RefreshCrc32(gpt);
+    EXPECT(GPT_SUCCESS == GptInit(gpt));
+    gpt->secondary_header[i] ^= 0xff;
+    RefreshCrc32(gpt);
+  }
+
+  /* change every char in signature of primary and secondary. Expect fail. */
+  for (i = 0; i < 8; ++i) {
+    gpt->primary_header[i] ^= 0xff;
+    gpt->secondary_header[i] ^= 0xff;
+    RefreshCrc32(gpt);
+    EXPECT(GPT_ERROR_INVALID_HEADERS == GptInit(gpt));
+    gpt->primary_header[i] ^= 0xff;
+    gpt->secondary_header[i] ^= 0xff;
+    RefreshCrc32(gpt);
+  }
+
+  return TEST_OK;
+}
+
 /* Tests if header CRC in two copies are calculated. */
 int HeaderCrcTest() {
   return TEST_FAIL;
@@ -45,7 +252,7 @@
   return TEST_FAIL;
 }
 
-/* Tests if GPTInit() handles non-identical partition entries well.
+/* Tests if GptInit() handles non-identical partition entries well.
  * Two copies of partition table entries must be identical. If not, we trust the
  * primary table entries, and mark secondary as modified (see Caller's write-
  * back order below). */
@@ -53,7 +260,7 @@
   return TEST_FAIL;
 }
 
-/* Tests if GPTInit() handles non-identical headers well.
+/* Tests if GptInit() handles non-identical headers well.
  * Two partition headers must be identical. If not, we trust the primary
  * partition header, and mark secondary as modified (see Caller's write-back
  * order below). */
@@ -84,7 +291,7 @@
   return TEST_FAIL;
 }
 
-/* Tests if GPTNextKernelEntry() can survive in different corrupt header/entries
+/* Tests if GptNextKernelEntry() can survive in different corrupt header/entries
  * combinations, like:
  *   primary GPT header         - valid
  *   primary partition table    - invalid
@@ -102,6 +309,8 @@
     test_func fp;
     int retval;
   } test_cases[] = {
+    { TEST_CASE(SignatureTest), },
+#if 0
     { TEST_CASE(HeaderCrcTest), },
     { TEST_CASE(MyLbaTest), },
     { TEST_CASE(SizeOfPartitionEntryTest), },
@@ -114,6 +323,7 @@
     { TEST_CASE(ValidEntryTest), },
     { TEST_CASE(NoOverlappedPartitionTest), },
     { TEST_CASE(CorruptCombinationTest), },
+#endif
   };
 
   for (i = 0; i < sizeof(test_cases)/sizeof(test_cases[0]); ++i) {
diff --git a/cgptlib/tests/cgpt_test.h b/cgptlib/tests/cgpt_test.h
index 0dcb637..4a8b115 100644
--- a/cgptlib/tests/cgpt_test.h
+++ b/cgptlib/tests/cgpt_test.h
@@ -7,7 +7,10 @@
 
 #include <stdio.h>
 
-#define TEST_FAIL -1
+enum {
+  TEST_FAIL = -1,
+  TEST_OK = 0,
+};
 
 /* ANSI Color coding sequences. */
 #define COL_GREEN "\e[1;32m"