Add script to diff test results between changes

Merge of http://go/wvgerrit/74965

It isn't always obvious which changes introduced test failures or fixes,
and similarly, it's unideal to have to manually run the tests for HEAD
and with a new change to determine the test diff, so this script runs it
for the last n changes, and diffs the test results by comparing the test
runs. It doesn't handle flaky tests, partly because I don't think it
can.

Change-Id: I5380abcb2f5bcadf172dba3c1270e4258e0c8a82

libwvdrmengine/diff_changes.sh

@@ -0,0 +1,92 @@
+#!/bin/bash
+
+set -e
+
+log_dir="${PWD}/diff_change_logs"
+rm -rf "${log_dir}"
+mkdir "${log_dir}"
+
+EXECUTABLE=""
+EXEC_ARGS=""
+NUM_CHANGES=-1
+while getopts "e:a:n:" opt; do
+  case "${opt}" in
+    e)
+      EXECUTABLE="${OPTARG}"
+      ;;
+    a)
+      EXEC_ARGS="${OPTARG}"
+      ;;
+    n)
+      NUM_CHANGES=${OPTARG}
+      ;;
+    \?)
+      echo "Usage: diff_changes.sh -e<build_and_test_executable> -a\"<executable_args>\" -n<number_of_changes>"
+      exit 1;
+      ;;
+  esac
+done
+
+if [ ! "${EXECUTABLE}" ] || [ "${NUM_CHANGES}" -lt 0 ]; then
+  echo "EXECUTABLE cannot be empty and NUM_CHANGES must be >= 0"
+  exit 1;
+else
+  EXECUTABLE="./${EXECUTABLE}"
+fi
+
+# We search for test cases by searching for lines that start with the RUN header
+# and FAILED or OK footers. Note that we capture the test name to make sure the
+# header and footer refer to the same test. We also exclude the header from
+# showing up again so we only match single tests.
+header="\[ RUN      \]"
+footer="(\[  FAILED  \]|\[       OK \])"
+test_regex="/(${header} ([\S]+)((?!${header})[\s\S])+${footer} \2) \([0-9]+ ms\)/g"
+
+while [ "${NUM_CHANGES}" -ge 0 ]; do
+  current_change="HEAD"
+  for i in $(seq 1 "${NUM_CHANGES}"); do
+    current_change="${current_change}^"
+  done
+  git checkout "${current_change}" >/dev/null
+  sha=$(git rev-parse HEAD)
+  run_exec="${EXECUTABLE} ${EXEC_ARGS}"
+  run_success=true
+  # Restore HEAD regardless if executable ran.
+  {
+    $run_exec |& tee "${log_dir}/build_and_test_results_${sha}.txt"
+  } || {
+    run_success=false
+  }
+  if [ "${current_change}" != "HEAD" ]; then
+    git checkout 'HEAD@{1}' >/dev/null
+  fi
+  if [ "${run_success}" = false ]; then
+    exit 1
+  fi
+  NUM_CHANGES=$((NUM_CHANGES - 1))
+done
+
+# Compute diffs of test results oldest first.
+file_list=$(find "${log_dir}" -type f -print0 | xargs -0 ls -tr)
+file_arr=($file_list)
+last_index=$((${#file_arr[@]} - 1));
+
+for current_index in "${!file_arr[@]}"; do
+  if [ "${current_index}" -lt "${last_index}" ]; then
+    next_index=$((current_index + 1))
+    first_sha=$(echo "${file_arr[current_index]}" | \
+      sed 's/.*build_and_test_results_\(.\+\).txt$/\1/')
+    second_sha=$(echo "${file_arr[next_index]}" | \
+      sed 's/.*build_and_test_results_\(.\+\).txt$/\1/')
+    output_diff="${log_dir}/test_diff_between_${second_sha}_and_${first_sha}"
+    perl_exec="perl -0777 -e                                                \
+              'open FILE, \$ARGV[0]; while (<FILE>) { \$file_text .= \$_; } \
+               while (\$file_text =~ ${test_regex}) {                       \
+                 print \"\$1\n\";                                           \
+               }'"
+    first_test_results=$(eval "${perl_exec} ${file_arr[current_index]}")
+    second_test_results=$(eval "${perl_exec} ${file_arr[next_index]}")
+    diff <(echo "${first_test_results}") <(echo "${second_test_results}") \
+      &> "${output_diff}"
+  fi
+done