diff --git a/scripts/test_paycheck.sh b/scripts/test_paycheck.sh
new file mode 100755
index 0000000..d6b9310
--- /dev/null
+++ b/scripts/test_paycheck.sh
@@ -0,0 +1,168 @@
+#!/bin/bash
+#
+# Copyright (c) 2013 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.
+
+# A test script for paycheck.py and the update_payload.py library.
+#
+# This script requires three payload files, along with a metadata signature for
+# each, and a public key for verifying signatures. Payload include:
+#
+# - A full payload for release X (old_full_payload)
+#
+# - A full payload for release Y (new_full_payload), where Y > X
+#
+# - A delta payload from X to Y (delta_payload)
+#
+# The test performs the following:
+#
+# - It verifies each payload against its metadata signature, also asserting the
+#   payload type. Another artifact is a human-readable payload report, which
+#   is output to stdout to be inspected by the user.
+#
+# - It performs a random block trace on the delta payload (both kernel and
+#   rootfs blocks), dumping the traces to stdout for the user to inspect.
+#
+# - It applies old_full_payload to yield old kernel (old_kern.part) and rootfs
+#   (old_root.part) partitions.
+#
+# - It applies delta_payload to old_{kern,root}.part to yield new kernel
+#   (new_delta_kern.part) and rootfs (new_delta_root.part) partitions.
+#
+# - It applies new_full_payload to yield reference new kernel
+#   (new_full_kern.part) and rootfs (new_full_root.part) partitions.
+#
+# - It compares new_{delta,full}_kern.part and new_{delta,full}_root.part to
+#   ensure that they are binary identical.
+#
+# If all steps have completed successfully we know with high certainty that
+# paycheck.py (and hence update_payload.py) correctly parses both full and
+# delta payloads, and applies them to yield the expected result. We also know
+# that tracing works, to the extent it does not crash. Manual inspection of
+# payload reports and block traces will improve this our confidence and are
+# strongly encouraged. Finally, each paycheck.py execution is timed.
+
+
+OLD_KERN_PART=old_kern.part
+OLD_ROOT_PART=old_root.part
+NEW_DELTA_KERN_PART=new_delta_kern.part
+NEW_DELTA_ROOT_PART=new_delta_root.part
+NEW_FULL_KERN_PART=new_full_kern.part
+NEW_FULL_ROOT_PART=new_full_root.part
+
+# Stop on errors, unset variables.
+set -e
+set -u
+
+log() {
+  echo "$@" >&2
+}
+
+die() {
+  log "$@"
+  exit 1
+}
+
+usage_and_exit() {
+  cat >&2 <<EOF
+Usage: ${0##*/} pubkey old_full_payload old_full_metasig \\
+         delta_payload delta_metasig new_full_payload new_full_metasig
+EOF
+  exit
+}
+
+check_payload() {
+  payload_file=$1
+  metasig_file=$2
+  payload_type=$3
+
+  time ${paycheck} -r - -k ${pubkey_file} -m ${metasig_file} \
+    -t ${payload_type} ${payload_file}
+}
+
+trace_kern_block() {
+  payload_file=$1
+  block=$2
+  time ${paycheck} -B ${block} ${payload_file}
+}
+
+trace_root_block() {
+  payload_file=$1
+  block=$2
+  time ${paycheck} -b ${block} ${payload_file}
+}
+
+apply_full_payload() {
+  payload_file=$1
+  dst_kern_part=$2
+  dst_root_part=$3
+
+  time ${paycheck} ${payload_file} ${dst_kern_part} ${dst_root_part}
+}
+
+apply_delta_payload() {
+  payload_file=$1
+  dst_kern_part=$2
+  dst_root_part=$3
+  src_kern_part=$4
+  src_root_part=$5
+
+  time ${paycheck} ${payload_file} ${dst_kern_part} ${dst_root_part} \
+    ${src_kern_part} ${src_root_part}
+}
+
+main() {
+  # Read command-line arguments.
+  if [ $# == 1 ] && [ "$1" == "-h" ]; then
+    usage_and_exit
+  elif [ $# != 7 ]; then
+    die "Error: unexpected number of arguments"
+  fi
+  pubkey_file="$1"
+  old_full_payload="$2"
+  old_full_metasig="$3"
+  delta_payload="$4"
+  delta_metasig="$5"
+  new_full_payload="$6"
+  new_full_metasig="$7"
+
+  # Find paycheck.py
+  paycheck=${0%/*}/paycheck.py
+  if [ -z "${paycheck}" ] || [ ! -x ${paycheck} ]; then
+    die "cannot find paycheck.py or file is not executable"
+  fi
+
+  log "Checking payloads..."
+  check_payload "${old_full_payload}" "${old_full_metasig}" full
+  check_payload "${new_full_payload}" "${new_full_metasig}" full
+  check_payload "${delta_payload}" "${delta_metasig}" delta
+  log "Done"
+
+  # Pick a random block between 0-1024
+  block=$((RANDOM * 1024 / 32767))
+  log "Tracing a random block (${block}) in full/delta payloads..."
+  trace_kern_block "${new_full_payload}" ${block}
+  trace_root_block "${new_full_payload}" ${block}
+  trace_kern_block "${delta_payload}" ${block}
+  trace_root_block "${delta_payload}" ${block}
+  log "Done"
+
+  log "Apply old full payload..."
+  apply_full_payload "${old_full_payload}" "${OLD_KERN_PART}" "${OLD_ROOT_PART}"
+  log "Done"
+  log "Apply delta payload to old partitions..."
+  time ./paycheck.py "${delta_payload}" "${NEW_DELTA_KERN_PART}" \
+    "${NEW_DELTA_ROOT_PART}" "${OLD_KERN_PART}" "${OLD_ROOT_PART}"
+  log "Done"
+  log "Apply new full payload..."
+  time ./paycheck.py "${new_full_payload}" "${NEW_FULL_KERN_PART}" \
+    "${NEW_FULL_ROOT_PART}"
+  log "Done"
+  log "Comparing results of delta and new full updates..."
+  diff "${NEW_FULL_KERN_PART}" "${NEW_DELTA_KERN_PART}"
+  diff "${NEW_FULL_ROOT_PART}" "${NEW_DELTA_ROOT_PART}"
+  log "Done"
+}
+
+main "$@"