diff --git a/scripts/test.sh b/scripts/test.sh
index c29a9aa9..03863c15 100755
--- a/scripts/test.sh
+++ b/scripts/test.sh
@@ -3,15 +3,16 @@
 source scripts/runtest.sh
 source scripts/portability.sh
 
-TOPDIR="$PWD"
-export FILES="$PWD"/tests/files
-
+# Kill child processes when we exit
 trap 'kill $(jobs -p) 2>/dev/null; exit 1' INT
 
-export PREFIX=generated/testdir
+# Create working directory
+TOPDIR="$PWD"
+export FILES="$PWD"/tests/files PREFIX=generated/testdir
 rm -rf "$PREFIX"
 mkdir -p "$PREFIX"/testdir
 
+# Populate working directory
 if [ -z "$TEST_HOST" ]
 then
   if [ $# -ne 0 ]
@@ -22,21 +23,25 @@ then
   fi
 fi
 
+# Add prefix to $PATH
 export -n PREFIX
 cd "$PREFIX"
-PATH="$PWD:$PATH"
-TESTDIR="$PWD"
+PATH="$PWD:$PATH" TESTDIR="$PWD"
 export LC_COLLATE=C
 
+# Collection OPTIONFLAGS for optional()
 [ -f "$TOPDIR/generated/config.h" ] &&
   export OPTIONFLAGS=:$($SED -nr 's/^#define CFG_(.*) 1$/\1/p' "$TOPDIR/generated/config.h" | tr '\n' :)
 
+# Run a test file in $TESTDIR/testdir with $CMDNAME and $C set, parse $FAILCOUNT
 do_test()
 {
+  # reset testdir
   cd "$TESTDIR" && rm -rf testdir continue && mkdir testdir && cd testdir ||
     exit 1
-  CMDNAME="${1##*/}"
-  CMDNAME="${CMDNAME%.test}"
+
+  # set CMDNAME to base name of test file, and C to full path to command
+  CMDNAME="${1##*/}" CMDNAME="${CMDNAME%.test}"
   if [ -z "$TEST_HOST" ]
   then
     C="$TESTDIR/$CMDNAME"
@@ -47,11 +52,13 @@ do_test()
     [ -z "$C" ] && printf '%s\n' "$SHOWSKIP: no $CMDNAME" && return
   fi
 
+  # Run command.test in a subshell
   (. "$1"; cd "$TESTDIR"; echo "$FAILCOUNT" > continue)
   cd "$TESTDIR"
   [ -e continue ] && FAILCOUNT=$(($(cat continue)+$FAILCOUNT)) || exit 1
 }
 
+# Run each test listed on command line or else all tests with executable bit set
 if [ $# -ne 0 ]
 then
   for i in "$@"