diff --git a/image_properties_android.cc b/image_properties_android.cc
index e815dbf..d52c40b 100644
--- a/image_properties_android.cc
+++ b/image_properties_android.cc
@@ -20,6 +20,7 @@
 
 #include <base/logging.h>
 #include <brillo/osrelease_reader.h>
+#include <brillo/strings/string_utils.h>
 #include <cutils/properties.h>
 
 #include "update_engine/common/boot_control_interface.h"
@@ -28,6 +29,8 @@
 #include "update_engine/common/prefs_interface.h"
 #include "update_engine/system_state.h"
 
+using std::string;
+
 namespace chromeos_update_engine {
 
 namespace {
@@ -47,10 +50,13 @@
 const char kPropBuildFingerprint[] = "ro.build.fingerprint";
 const char kPropBuildType[] = "ro.build.type";
 
-std::string GetStringWithDefault(const brillo::OsReleaseReader& osrelease,
-                                 const std::string& key,
-                                 const std::string& default_value) {
-  std::string result;
+// A prefix added to the path, used for testing.
+const char* root_prefix = nullptr;
+
+string GetStringWithDefault(const brillo::OsReleaseReader& osrelease,
+                            const string& key,
+                            const string& default_value) {
+  string result;
   if (osrelease.GetString(key, &result))
     return result;
   LOG(INFO) << "Cannot load ImageProperty " << key << ", using default value "
@@ -61,25 +67,35 @@
 }  // namespace
 
 namespace test {
-void SetImagePropertiesRootPrefix(const char* /* test_root_prefix */) {}
+void SetImagePropertiesRootPrefix(const char* test_root_prefix) {
+  root_prefix = test_root_prefix;
+}
 }  // namespace test
 
 ImageProperties LoadImageProperties(SystemState* system_state) {
   ImageProperties result;
 
   brillo::OsReleaseReader osrelease;
-  osrelease.Load();
+  if (root_prefix)
+    osrelease.LoadTestingOnly(base::FilePath(root_prefix));
+  else
+    osrelease.Load();
   result.product_id =
       GetStringWithDefault(osrelease, kProductId, "invalid-product");
   result.system_id = GetStringWithDefault(
       osrelease, kSystemId, "developer-boards:brillo-starter-board");
+  // Update the system id to match the prefix of product id for testing.
+  string prefix, not_used, system_id;
+  if (brillo::string_utils::SplitAtFirst(
+          result.product_id, ":", &prefix, &not_used, false) &&
+      brillo::string_utils::SplitAtFirst(
+          result.system_id, ":", &not_used, &system_id, false)) {
+    result.system_id = prefix + ":" + system_id;
+  }
   result.canary_product_id = result.product_id;
-  std::string system_version =
+  result.version = GetStringWithDefault(osrelease, kProductVersion, "0.0.0.0");
+  result.system_version =
       GetStringWithDefault(osrelease, kSystemVersion, "0.0.0.0");
-  std::string product_version =
-      GetStringWithDefault(osrelease, kProductVersion, "0.0.0.0");
-  result.version = product_version;
-  result.system_version = system_version;
 
   char prop[PROPERTY_VALUE_MAX];
   property_get(kPropProductName, prop, "brillo");
@@ -95,10 +111,10 @@
   // channel where we got the image from in prefs at the time of the update, so
   // we use that as the current channel if available. During provisioning, there
   // is no value assigned, so we default to the "stable-channel".
-  std::string current_channel_key =
+  string current_channel_key =
       kPrefsChannelOnSlotPrefix +
       std::to_string(system_state->boot_control()->GetCurrentSlot());
-  std::string current_channel;
+  string current_channel;
   if (!system_state->prefs()->Exists(current_channel_key) ||
       !system_state->prefs()->GetString(current_channel_key, &current_channel))
     current_channel = "stable-channel";