diff --git a/Makefile b/Makefile
index 986856d..718b319 100644
--- a/Makefile
+++ b/Makefile
@@ -69,7 +69,6 @@ unlock-rpm:
 confidence:
 	@if [[ -e ~/.gnupg ]]; then echo ERROR: '~/.gnupg should not exist. If it does, bugs may polute your .gnupg configuration. If the code has no bugs everything will be fine. Do you feel lucky?'; false ; fi
 	@if which >/dev/null gpg-agent ; then pkill gpg-agent ; rm -rf /tmp/tmp.* ; fi
-	@export PATH=~/gitwork/blackbox/bin:/usr/local/bin:/bin:/usr/bin:/usr/local/sbin:/usr/sbin:/sbin ; 
-		cd ~/gitwork/blackbox && tools/confidence_test.sh
+	@export PATH=~/gitwork/blackbox/bin:/usr/local/bin:/bin:/usr/bin:/usr/local/sbin:/usr/sbin:/sbin:/opt/local/bin ; tools/confidence_test.sh
 	@if which >/dev/null gpg-agent ; then pkill gpg-agent ; fi
 	@if [[ -e ~/.gnupg ]]; then echo ERROR: '~/.gnupg was created which means the scripts might be poluting GnuPG configuration.  Fix this bug.'; false ; fi
diff --git a/tools/confidence_test.sh b/tools/confidence_test.sh
index 8205699..216f49a 100755
--- a/tools/confidence_test.sh
+++ b/tools/confidence_test.sh
@@ -1,7 +1,7 @@
 #!/usr/bin/env bash
 
 blackbox_home=$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )/../bin
-export PATH=${blackbox_home}:/usr/local/bin:/bin:/usr/bin:/usr/local/sbin:/usr/sbin:/sbin
+export PATH="${blackbox_home}:/usr/local/bin:/bin:/usr/bin:/usr/local/sbin:/usr/sbin:/sbin:/opt/local/bin"
 
 . _stack_lib.sh
 
@@ -15,6 +15,25 @@ function PHASE() {
   echo '********************'
 }
 
+function md5sum_file() {
+  # Portably generate the MD5 hash of file $1.
+  case $(uname -s) in
+    Darwin )
+      md5 -r "$1" | awk '{ print $1 }'
+      ;;
+    Linux )
+      md5sum "$1" | awk '{ print $1 }'
+      ;;
+    CYGWIN* )
+      md5sum "$1" | awk '{ print $1 }'
+      ;;
+    * )
+      echo 'ERROR: Unknown OS. Exiting.'
+      exit 1
+      ;;
+  esac
+}
+
 function assert_file_missing() {
   if [[ -e "$1" ]]; then
     echo "ASSERT FAILED: ${1} should not exist."
@@ -36,7 +55,7 @@ function assert_file_md5hash() {
   local file="$1"
   local wanted="$2"
   assert_file_exists "$file"
-  local found=$(md5sum <"$file" | cut -d' ' -f1 )
+  local found=$(md5sum_file "$file")
   if [[ "$wanted" != "$found" ]]; then
     echo "ASSERT FAILED: $file hash wanted=$wanted found=$found"
     exit 1
@@ -54,7 +73,7 @@ function assert_file_group() {
       ;;
   esac
 
-  local found=$(ls -l "$file" | awk '{ print $4 }')
+  local found=$(ls -lg "$file" | awk '{ print $3 }')
   # NB(tlim): We could do this with 'stat' but it would break on BSD-style OSs.
   if [[ "$wanted" != "$found" ]]; then
     echo "ASSERT FAILED: $file chgrp wanted=$wanted found=$found"
@@ -220,6 +239,7 @@ gpg --import keyrings/live/pubring.gpg
 TEST_GID_NUM=$(id -G | fmt -1 | tail -n +2 | grep -xv $(id -u) | head -n 1)
 TEST_GID_NAME=$(getent group "$TEST_GID_NUM" | cut -d: -f1)
 DEFAULT_GID_NAME=$(getent group $(id -u) | cut -d: -f1)
+: ${DEFAULT_GID_NAME:=staff) ;
 echo TEST_GID_NUM=$TEST_GID_NUM
 echo TEST_GID_NAME=$TEST_GID_NAME
 echo DEFAULT_GID_NAME=$DEFAULT_GID_NAME