Rely on Portage to run required stages before "test" stage.

cros_run_unit_tests

 #!/bin/bash
 
 # 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.
 
 # This script builds and runs Chromium OS unit tests.  Note that this script
 # utilizes the src_test stanza in chromeos-base packages.  These stanzas
 # should both build and run the unit tests.
 
@@ skipping 29 matching lines @@
 
 function check_src_test() {
   egrep '^src_test()' "${1}" > /dev/null
 }
 
 function record_test_failure() {
   TEST_FAILURES=$(( TEST_FAILURES + 1 ))
   FAILED_PACKAGES="${FAILED_PACKAGES} ${1}"
 }
 
+# Run the unit test for the given package, via ebuild src_test() function.
 function run_unit_test() {
-  FEATURES="-buildpkg -digest noauto" \
-    ebuild-${FLAGS_board} "${1}" clean unpack prepare configure test
+  FEATURES="-buildpkg -digest" \
+    ebuild-${FLAGS_board} "${1}" clean test clean
 }
 
 # Parse command line and die if unexpected parameters given.
 FLAGS_HELP="usage: ${0} [flags]"
 FLAGS "${@}" || exit 1
 eval set -- "${FLAGS_ARGV}"
 check_flags_only_and_allow_null_arg "${@}" && set --
 
 set -e
 
@@ skipping 45 matching lines @@
   warn "${NO_UNITTESTS}"
 fi
 
 if [ ${TEST_FAILURES} -ne 0 ]; then
   error "Run completed with ${TEST_FAILURES}/${TEST_COUNT} test failures."
   error "Following packages had failing tests:"
   die "${FAILED_PACKAGES}"
 else
   info "All unit tests passed."
 fi