Don't print an error message about cat if a test exits abnormally

On calls to fail, the failure message is written to $TEST_TMPDIR/__fail. This
is cat-ed to get the message, but if the test exited without calling fail then
an annoying 'cat: blah/blah/blah/__fail: No such file or directory' message is
printed.  This throws out the error message if the cat fails.

--
MOS_MIGRATED_REVID=109896051

src/test/shell/testenv.sh

@@ -122,9 +122,9 @@ if [ -z "${TEST_TMPDIR:-}" ]; then
 fi
 if [ ! -e "${TEST_TMPDIR}" ]; then
   mkdir -p -m 0700 "${TEST_TMPDIR}"
+  # Clean TEST_TMPDIR on exit
+  atexit "rm -fr ${TEST_TMPDIR}"
 fi
-# Clean TEST_TMPDIR on exit
-atexit "rm -fr ${TEST_TMPDIR}"
 
 # Functions to compare the actual output of a test to the expected
 # (golden) output.

src/test/shell/unittest.bash

@@ -531,8 +531,8 @@ function run_suite() {
           timestamp >$TEST_TMPDIR/__ts_start
           set_up
           eval $TEST_name
-          timestamp >$TEST_TMPDIR/__ts_end
           tear_down
+          timestamp >$TEST_TMPDIR/__ts_end
           test $TEST_passed == true
         ) 2>&1 | tee $TEST_TMPDIR/__log
         # Note that tee will prevent the control flow continuing if the test
@@ -570,7 +570,7 @@ function run_suite() {
         echo "FAILED: $TEST_name" >&2
         # end marker in CDATA cannot be escaped, we need to split the CDATA sections
         log=$(cat $TEST_TMPDIR/__log | sed 's/]]>/]]>]]&gt;<![CDATA[/g')
-        fail_msg=$(cat $TEST_TMPDIR/__fail || echo "No failure message")
+        fail_msg=$(cat $TEST_TMPDIR/__fail 2> /dev/null || echo "No failure message")
         testcase_tag="<testcase name=\"$TEST_name\" status=\"run\" time=\"$run_time\" classname=\"\"><error message=\"$fail_msg\"><![CDATA[$log]]></error></testcase>"
       fi
       $TEST_verbose && echo >&2

src/test/shell/unittest_test.sh

@@ -20,6 +20,16 @@
 DIR=$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)
 source ${DIR}/unittest.bash || { echo "Could not source unittest.sh" >&2; exit 1; }
 
+function set_up() {
+  tmp_TEST_TMPDIR=$TEST_TMPDIR
+  TEST_TMPDIR=$TEST_TMPDIR/$TEST_name
+  mkdir -p $TEST_TMPDIR
+}
+
+function tear_down() {
+  TEST_TMPDIR=$tmp_TEST_TMPDIR
+}
+
 function test_1() {
   echo "Everything is okay in test_1"
 }
@@ -36,4 +46,40 @@ function test_timestamp() {
   assert_equals $time_diff 123.456
 }
 
+function test_failure_message() {
+  cd $TEST_TMPDIR
+  cat > thing.sh <<EOF
+#!/bin/bash
+source ${DIR}/unittest.bash
+
+function test_thing() {
+  fail "I'm a failure"
+}
+
+run_suite "thing tests"
+EOF
+  chmod +x thing.sh
+  ./thing.sh &> $TEST_log || echo "thing.sh should fail"
+  expect_not_log "__fail: No such file or directory"
+  assert_contains "I'm a failure." $XML_OUTPUT_FILE
+}
+
+function test_no_failure_message() {
+  cd $TEST_TMPDIR
+  cat > thing.sh <<EOF
+#!/bin/bash
+source ${DIR}/unittest.bash
+
+function test_thing() {
+  TEST_passed=blorp
+}
+
+run_suite "thing tests"
+EOF
+  chmod +x thing.sh
+  ./thing.sh &> $TEST_log || echo "thing.sh should fail"
+  expect_not_log "__fail: No such file or directory"
+  assert_contains "No failure message" $XML_OUTPUT_FILE
+}
+
 run_suite "unittests Tests"