Add comments to testcase.sh.

tests/testcase.sh

@@ -4,23 +4,29 @@ set -ueo pipefail
 # A simple testcase runner that runs a command, captures all its command-line
 # outputs, and compares them against expected outputs.
 
+# Command-line parsing; this script is meant to be run from a # higher-level
+# script, so don't do anything fancy.
 runwasi="$1"
 clang="$2"
 options="$3"
 input="$4"
 
+# Compile names for generated files.
 wasm="$input.$options.wasm"
 stdout_observed="$input.$options.stdout.observed"
 stderr_observed="$input.$options.stderr.observed"
 exit_status_observed="$input.$options.exit_status.observed"
 
+# Optionally load compiler options from a file.
 if [ -e "$input.options" ]; then
-    file_options=$(cat "$inpit.options")
+    file_options=$(cat "$input.options")
 else
     file_options=
 fi
 
 echo "Testing $input..."
+
+# Determine the input file to write to stdin.
 "$clang" $options $file_options "$input" -o "$wasm"
 if [ -e "$input.stdin" ]; then
   stdin="$input.stdin"
@@ -28,6 +34,7 @@ else
   stdin="/dev/null"
 fi
 
+# Run the test, capturing stdout, stderr, and the exit status.
 exit_status=0
 "$runwasi" "$wasm" \
     < "$stdin" \
@@ -36,6 +43,7 @@ exit_status=0
     || exit_status=$?
 echo $exit_status > "$exit_status_observed"
 
+# Determine the reference files to compare with.
 if [ -e "$input.stdout.expected" ]; then
   stdout_expected="$input.stdout.expected"
 else
@@ -52,6 +60,8 @@ else
   exit_status_expected=../exit_status_zero
 fi
 
+# If there are any differences, diff will return a non-zero exit status, and
+# since this script uses "set -e", it will return a non-zero exit status too.
 diff -u "$stderr_expected" "$stderr_observed"
 diff -u "$stdout_expected" "$stdout_observed"
 diff -u "$exit_status_expected" "$exit_status_observed"