diff --git a/test_utils.cc b/test_utils.cc
index 6255119..6346bf3 100644
--- a/test_utils.cc
+++ b/test_utils.cc
@@ -2,72 +2,273 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include "update_engine/test_utils.h"
 #include <sys/stat.h>
 #include <sys/types.h>
+#include <errno.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <unistd.h>
+#include <set>
 #include <string>
 #include <vector>
-#include "update_engine/test_utils.h"
-#include "base/logging.h"
+#include "base/string_util.h"
+#include "chromeos/obsolete_logging.h"
 
 #include "update_engine/file_writer.h"
+#include "update_engine/filesystem_iterator.h"
+#include "update_engine/utils.h"
 
+using std::set;
 using std::string;
 using std::vector;
 
 namespace chromeos_update_engine {
 
-vector<char> ReadFile(const string& path) {
-  vector<char> ret;
-  FILE* fp = fopen(path.c_str(), "r");
-  if (!fp)
-    return ret;
-  const size_t kChunkSize(1024);
-  size_t read_size;
-  do {
-    char buf[kChunkSize];
-    read_size = fread(buf, 1, kChunkSize, fp);
-    ret.insert(ret.end(), buf, buf + read_size);
-  } while (read_size == kChunkSize);
-  fclose(fp);
-  return ret;
+bool WriteFile(const char* path, const char* data, int data_len) {
+  DirectFileWriter writer;
+  TEST_AND_RETURN_FALSE_ERRNO(0 == writer.Open(path,
+                                               O_WRONLY | O_CREAT | O_TRUNC,
+                                               0666));
+  ScopedFileWriterCloser closer(&writer);
+  TEST_AND_RETURN_FALSE_ERRNO(data_len == writer.Write(data, data_len));
+  return true;
 }
 
-bool WriteFile(const std::string& path, const std::vector<char>& data) {
-  DirectFileWriter writer;
-  if (0 != writer.Open(path.c_str(), O_WRONLY | O_CREAT | O_TRUNC, 0644)) {
-    return false;
-  }
-  if (static_cast<int>(data.size()) != writer.Write(&data[0], data.size())) {
-    writer.Close();
-    return false;
-  }
-  writer.Close();
-  return true;
+bool WriteFileVector(const std::string& path, const std::vector<char>& data) {
+  return WriteFile(path.c_str(), &data[0], data.size());
+}
+
+bool WriteFileString(const std::string& path, const std::string& data) {
+  return WriteFile(path.c_str(), data.data(), data.size());
 }
 
 off_t FileSize(const string& path) {
   struct stat stbuf;
   int rc = stat(path.c_str(), &stbuf);
-  CHECK_EQ(0, rc);
+  CHECK_EQ(rc, 0);
   if (rc < 0)
     return rc;
   return stbuf.st_size;
 }
 
+std::string Readlink(const std::string& path) {
+  vector<char> buf(PATH_MAX + 1);
+  ssize_t r = readlink(path.c_str(), &buf[0], buf.size());
+  if (r < 0)
+    return "";
+  CHECK_LT(r, static_cast<ssize_t>(buf.size()));
+  buf.resize(r);
+  string ret;
+  ret.insert(ret.begin(), buf.begin(), buf.end());
+  return ret;
+}
+
 std::vector<char> GzipCompressData(const std::vector<char>& data) {
   const char fname[] = "/tmp/GzipCompressDataTemp";
-  if (!WriteFile(fname, data)) {
+  if (!WriteFileVector(fname, data)) {
     system((string("rm ") + fname).c_str());
     return vector<char>();
   }
   system((string("cat ") + fname + "|gzip>" + fname + ".gz").c_str());
   system((string("rm ") + fname).c_str());
-  vector<char> ret = ReadFile(string(fname) + ".gz");
+  vector<char> ret;
+  EXPECT_TRUE(utils::ReadFile(string(fname) + ".gz", &ret));
   system((string("rm ") + fname + ".gz").c_str());
   return ret;
 }
 
+vector<char> GenerateSampleMbr() {
+  // This is the actual MBR from my dev machine. Partition 1 (the first)
+  // is currently marked bootable
+  char mbr[512] = {
+    0xeb, 0x48, 0x90, 0x10, 0x8e, 0xd0, 0xbc, 0x00,
+    0xb0, 0xb8, 0x00, 0x00, 0x8e, 0xd8, 0x8e, 0xc0,
+    0xfb, 0xbe, 0x00, 0x7c, 0xbf, 0x00, 0x06, 0xb9,
+    0x00, 0x02, 0xf3, 0xa4, 0xea, 0x21, 0x06, 0x00,
+    0x00, 0xbe, 0xbe, 0x07, 0x38, 0x04, 0x75, 0x0b,
+    0x83, 0xc6, 0x10, 0x81, 0xfe, 0xfe, 0x07, 0x75,
+    0xf3, 0xeb, 0x16, 0xb4, 0x02, 0xb0, 0x01, 0xbb,
+    0x00, 0x7c, 0xb2, 0x80, 0x8a, 0x74, 0x03, 0x02,
+    0xff, 0x00, 0x00, 0x20, 0x01, 0x00, 0x00, 0x00,
+    0x00, 0x02, 0xfa, 0x90, 0x90, 0xf6, 0xc2, 0x80,
+    0x75, 0x02, 0xb2, 0x80, 0xea, 0x59, 0x7c, 0x00,
+    0x00, 0x31, 0xc0, 0x8e, 0xd8, 0x8e, 0xd0, 0xbc,
+    0x00, 0x20, 0xfb, 0xa0, 0x40, 0x7c, 0x3c, 0xff,
+    0x74, 0x02, 0x88, 0xc2, 0x52, 0xbe, 0x7f, 0x7d,
+    0xe8, 0x34, 0x01, 0xf6, 0xc2, 0x80, 0x74, 0x54,
+    0xb4, 0x41, 0xbb, 0xaa, 0x55, 0xcd, 0x13, 0x5a,
+    0x52, 0x72, 0x49, 0x81, 0xfb, 0x55, 0xaa, 0x75,
+    0x43, 0xa0, 0x41, 0x7c, 0x84, 0xc0, 0x75, 0x05,
+    0x83, 0xe1, 0x01, 0x74, 0x37, 0x66, 0x8b, 0x4c,
+    0x10, 0xbe, 0x05, 0x7c, 0xc6, 0x44, 0xff, 0x01,
+    0x66, 0x8b, 0x1e, 0x44, 0x7c, 0xc7, 0x04, 0x10,
+    0x00, 0xc7, 0x44, 0x02, 0x01, 0x00, 0x66, 0x89,
+    0x5c, 0x08, 0xc7, 0x44, 0x06, 0x00, 0x70, 0x66,
+    0x31, 0xc0, 0x89, 0x44, 0x04, 0x66, 0x89, 0x44,
+    0x0c, 0xb4, 0x42, 0xcd, 0x13, 0x72, 0x05, 0xbb,
+    0x00, 0x70, 0xeb, 0x7d, 0xb4, 0x08, 0xcd, 0x13,
+    0x73, 0x0a, 0xf6, 0xc2, 0x80, 0x0f, 0x84, 0xea,
+    0x00, 0xe9, 0x8d, 0x00, 0xbe, 0x05, 0x7c, 0xc6,
+    0x44, 0xff, 0x00, 0x66, 0x31, 0xc0, 0x88, 0xf0,
+    0x40, 0x66, 0x89, 0x44, 0x04, 0x31, 0xd2, 0x88,
+    0xca, 0xc1, 0xe2, 0x02, 0x88, 0xe8, 0x88, 0xf4,
+    0x40, 0x89, 0x44, 0x08, 0x31, 0xc0, 0x88, 0xd0,
+    0xc0, 0xe8, 0x02, 0x66, 0x89, 0x04, 0x66, 0xa1,
+    0x44, 0x7c, 0x66, 0x31, 0xd2, 0x66, 0xf7, 0x34,
+    0x88, 0x54, 0x0a, 0x66, 0x31, 0xd2, 0x66, 0xf7,
+    0x74, 0x04, 0x88, 0x54, 0x0b, 0x89, 0x44, 0x0c,
+    0x3b, 0x44, 0x08, 0x7d, 0x3c, 0x8a, 0x54, 0x0d,
+    0xc0, 0xe2, 0x06, 0x8a, 0x4c, 0x0a, 0xfe, 0xc1,
+    0x08, 0xd1, 0x8a, 0x6c, 0x0c, 0x5a, 0x8a, 0x74,
+    0x0b, 0xbb, 0x00, 0x70, 0x8e, 0xc3, 0x31, 0xdb,
+    0xb8, 0x01, 0x02, 0xcd, 0x13, 0x72, 0x2a, 0x8c,
+    0xc3, 0x8e, 0x06, 0x48, 0x7c, 0x60, 0x1e, 0xb9,
+    0x00, 0x01, 0x8e, 0xdb, 0x31, 0xf6, 0x31, 0xff,
+    0xfc, 0xf3, 0xa5, 0x1f, 0x61, 0xff, 0x26, 0x42,
+    0x7c, 0xbe, 0x85, 0x7d, 0xe8, 0x40, 0x00, 0xeb,
+    0x0e, 0xbe, 0x8a, 0x7d, 0xe8, 0x38, 0x00, 0xeb,
+    0x06, 0xbe, 0x94, 0x7d, 0xe8, 0x30, 0x00, 0xbe,
+    0x99, 0x7d, 0xe8, 0x2a, 0x00, 0xeb, 0xfe, 0x47,
+    0x52, 0x55, 0x42, 0x20, 0x00, 0x47, 0x65, 0x6f,
+    0x6d, 0x00, 0x48, 0x61, 0x72, 0x64, 0x20, 0x44,
+    0x69, 0x73, 0x6b, 0x00, 0x52, 0x65, 0x61, 0x64,
+    0x00, 0x20, 0x45, 0x72, 0x72, 0x6f, 0x72, 0x00,
+    0xbb, 0x01, 0x00, 0xb4, 0x0e, 0xcd, 0x10, 0xac,
+    0x3c, 0x00, 0x75, 0xf4, 0xc3, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x50, 0xc1, 0x04, 0x00, 0x00, 0x00, 0x80, 0x01,
+    0x01, 0x00, 0x83, 0xfe, 0xff, 0xff, 0x3f, 0x00,
+    0x00, 0x00, 0x09, 0x7f, 0x32, 0x06, 0x00, 0xfe,
+    0xff, 0xff, 0x05, 0xfe, 0xff, 0xff, 0x48, 0x7f,
+    0x32, 0x06, 0x79, 0x59, 0x2d, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x55, 0xaa
+  };
+  vector<char> ret;
+  ret.insert(ret.begin(), mbr, mbr + sizeof(mbr));
+  return ret;
+}
+
+std::string GetUnusedLoopDevice() {
+  // get a loop device we can use for the install device
+  FILE* find_dev_cmd = popen("losetup -f", "r");
+  CHECK(find_dev_cmd);
+
+  string ret;
+  char dev[100] = {0};
+  size_t r;
+  while ((r = fread(dev, 1, sizeof(dev - 1), find_dev_cmd)) > 0) {
+    EXPECT_LT(r, sizeof(dev));
+    ret.insert(ret.end(), dev, dev + r);
+  }
+  EXPECT_EQ(r, 0);
+  EXPECT_TRUE(feof(find_dev_cmd));
+  fclose(find_dev_cmd);
+
+  // strip trailing \n on dev
+  if (*ret.rbegin() == '\n')
+    ret.resize(ret.size() - 1);
+
+  return ret;
+}
+
+bool ExpectVectorsEq(const vector<char>& a, const vector<char>& b) {
+  EXPECT_EQ(a.size(), b.size());
+  if (a.size() != b.size())
+    return false;
+  for (unsigned int i = 0; i < a.size(); i++) {
+    EXPECT_EQ(a[i], b[i]) << "offset: " << i;
+  }
+  return true;
+}
+
+void CreateExtImageAtPath(const string& path, vector<string>* out_paths) {
+  // create 10MiB sparse file
+  const char* const mount_path = kMountPath.c_str();
+  EXPECT_EQ(0, System(StringPrintf("dd if=/dev/zero of=%s"
+                                   " seek=10485759 bs=1 count=1",
+                                   path.c_str())));
+  EXPECT_EQ(0, System(StringPrintf("mkfs.ext3 -F %s", path.c_str())));
+  EXPECT_EQ(0, System(StringPrintf("mkdir -p %s", mount_path)));
+  EXPECT_EQ(0, System(StringPrintf("mount -o loop %s %s", path.c_str(),
+                                   mount_path)));
+  EXPECT_EQ(0, System(StringPrintf("echo hi > %s/hi", mount_path)));
+  EXPECT_EQ(0, System(StringPrintf("echo hello > %s/hello", mount_path)));
+  EXPECT_EQ(0, System(StringPrintf("mkdir %s/some_dir", mount_path)));
+  EXPECT_EQ(0, System(StringPrintf("mkdir %s/some_dir/empty_dir", mount_path)));
+  EXPECT_EQ(0, System(StringPrintf("mkdir %s/some_dir/mnt", mount_path)));
+  EXPECT_EQ(0, System(StringPrintf("echo T > %s/some_dir/test", mount_path)));
+  EXPECT_EQ(0, System(StringPrintf("mkfifo %s/some_dir/fifo", mount_path)));
+  EXPECT_EQ(0, System(StringPrintf("mknod %s/cdev c 2 3", mount_path)));
+  EXPECT_EQ(0, System(StringPrintf("ln -s /some/target %s/sym", mount_path)));
+  EXPECT_EQ(0, System(StringPrintf("ln %s/some_dir/test %s/testlink",
+                                   mount_path, mount_path)));
+  EXPECT_EQ(0, System(StringPrintf("umount %s", mount_path)));
+  
+  if (out_paths) {
+    out_paths->clear();
+    out_paths->push_back("");
+    out_paths->push_back("/hi");
+    out_paths->push_back("/hello");
+    out_paths->push_back("/some_dir");
+    out_paths->push_back("/some_dir/empty_dir");
+    out_paths->push_back("/some_dir/mnt");
+    out_paths->push_back("/some_dir/test");
+    out_paths->push_back("/some_dir/fifo");
+    out_paths->push_back("/cdev");
+    out_paths->push_back("/testlink");
+    out_paths->push_back("/sym");
+    out_paths->push_back("/lost+found");
+  }
+}
+
+void VerifyAllPaths(const string& parent, set<string> expected_paths) {
+  FilesystemIterator iter(parent, set<string>());
+  ino_t test_ino = 0;
+  ino_t testlink_ino = 0;
+  while (!iter.IsEnd()) {
+    string path = iter.GetFullPath();
+    EXPECT_TRUE(expected_paths.find(path) != expected_paths.end()) << path;
+    EXPECT_EQ(1, expected_paths.erase(path));
+    if (utils::StringHasSuffix(path, "/hi") ||
+        utils::StringHasSuffix(path, "/hello") ||
+        utils::StringHasSuffix(path, "/test") ||
+        utils::StringHasSuffix(path, "/testlink")) {
+      EXPECT_TRUE(S_ISREG(iter.GetStat().st_mode));
+      if (utils::StringHasSuffix(path, "/test"))
+        test_ino = iter.GetStat().st_ino;
+      else if (utils::StringHasSuffix(path, "/testlink"))
+        testlink_ino = iter.GetStat().st_ino;
+    } else if (utils::StringHasSuffix(path, "/some_dir") ||
+               utils::StringHasSuffix(path, "/empty_dir") ||
+               utils::StringHasSuffix(path, "/mnt") ||
+               utils::StringHasSuffix(path, "/lost+found") ||
+               parent == path) {
+      EXPECT_TRUE(S_ISDIR(iter.GetStat().st_mode));
+    } else if (utils::StringHasSuffix(path, "/fifo")) {
+      EXPECT_TRUE(S_ISFIFO(iter.GetStat().st_mode));
+    } else if (utils::StringHasSuffix(path, "/cdev")) {
+      EXPECT_TRUE(S_ISCHR(iter.GetStat().st_mode));
+    } else if (utils::StringHasSuffix(path, "/sym")) {
+      EXPECT_TRUE(S_ISLNK(iter.GetStat().st_mode));
+    } else {
+      LOG(INFO) << "got non hardcoded path: " << path;
+    }
+    iter.Increment();
+  }
+  EXPECT_EQ(testlink_ino, test_ino);
+  EXPECT_NE(0, test_ino);
+  EXPECT_FALSE(iter.IsErr());
+  EXPECT_TRUE(expected_paths.empty());
+  if (!expected_paths.empty()) {
+    for (set<string>::const_iterator it = expected_paths.begin();
+         it != expected_paths.end(); ++it) {
+      LOG(INFO) << "extra path: " << *it;
+    }
+  }
+}
+
 }  // namespace chromeos_update_engine