diff --git a/test/shell/test_cross_build.sh b/test/shell/test_cross_build.sh
index 5efe07fb6..023012432 100644
--- a/test/shell/test_cross_build.sh
+++ b/test/shell/test_cross_build.sh
@@ -9,11 +9,11 @@ cd test_cross_build
 
 function test_cross_build() {
   bazel test //...
-  bazel clean
-  bazel shutdown;
 }
 
 function test_scalafmt() {
+  bazel build //scalafmt/...
+
   run_formatting scalafmt binary2 binary2
   run_formatting scalafmt binary3 binary3
   run_formatting scalafmt library2 library2
@@ -24,3 +24,10 @@ function test_scalafmt() {
 
 $runner test_cross_build
 $runner test_scalafmt
+
+# `bazel shutdown` used to be in `test_cross_build`, after a `bazel clean`.
+# However, the protobuf library tends to rebuild frequently. Not cleaning and
+# postponing the shutdown to the end of the script helps avoid rebuilding as
+# often, speeding up the tests. It also potentially speeds up debugging by
+# preserving the workspace state when a test fails.
+bazel shutdown
diff --git a/test/shell/test_runner.sh b/test/shell/test_runner.sh
index 501793996..db3a7aa68 100644
--- a/test/shell/test_runner.sh
+++ b/test/shell/test_runner.sh
@@ -13,9 +13,10 @@ run_test_ci() {
   echo "running test $TEST_ARG"
   eval $TEST_ARG &>$log_file &
   local test_pid=$!
+
   SECONDS=0
-  TIMOUT=${TEST_TIMEOUT-60}
-  test_pulse_printer $! $TIMOUT $TEST_ARG &
+  test_pulse_printer "$test_pid" "${TEST_TIMEOUT:-60}" $TEST_ARG &
+
   local pulse_printer_pid=$!
   local result
 
@@ -25,7 +26,7 @@ run_test_ci() {
     kill $pulse_printer_pid && wait $pulse_printer_pid 2>/dev/null || true
   } || return 1
 
-  DURATION=$SECONDS
+  local DURATION=$SECONDS
   if [ $result -eq 0 ]; then
     echo -e "\n${GREEN}Test \"$TEST_ARG\" successful ($DURATION sec) $NC"
   else
@@ -38,9 +39,9 @@ run_test_ci() {
 
 test_pulse_printer() {
   # makes sure something is printed to stdout while test is running
-  local test_pid=$1
+  local test_pid="$1"
   shift
-  local timeout=$1 # in minutes
+  local timeout="$1" # in minutes
   shift
   local count=0
 
@@ -60,24 +61,42 @@ test_pulse_printer() {
 run_test_local() {
   # runs the tests locally
   set +e
-  SECONDS=0
-  TEST_ARG=$@
+  local TEST_ARG=$@
+  local RES=''
+
+  # This allows us to run a single test case with full Bazel output without
+  # having to search for it and recreate its command line.
+  if [[ -n "$RULES_SCALA_TEST_ONLY" &&
+        "$TEST_ARG" != "$RULES_SCALA_TEST_ONLY" ]]; then
+    return
+  fi
+
   echo "running test $TEST_ARG"
-  RES=$($TEST_ARG 2>&1)
-  RESPONSE_CODE=$?
-  DURATION=$SECONDS
+  SECONDS=0
+
+  if [[ -n "$RULES_SCALA_TEST_VERBOSE" || -n "$RULES_SCALA_TEST_ONLY" ]]; then
+    $TEST_ARG
+  else
+    RES="$($TEST_ARG 2>&1)"
+  fi
+
+  local RESPONSE_CODE="$?"
+  local DURATION="$SECONDS"
+
   if [ $RESPONSE_CODE -eq 0 ]; then
     echo -e "${GREEN} Test \"$TEST_ARG\" successful ($DURATION sec) $NC"
   else
-    echo -e "\nLog:\n"
-    echo "$RES"
+    if [[ -n "$RES" ]]; then
+      echo -e "\nLog:\n"
+      echo "$RES"
+    fi
     echo -e "${RED} Test \"$TEST_ARG\" failed $NC ($DURATION sec) $NC"
     exit $RESPONSE_CODE
   fi
 }
 
 get_test_runner() {
-  test_env=$1
+  local test_env="$1"
   if [[ "${test_env}" != "ci" && "${test_env}" != "local" ]]; then
     echo -e "${RED}test_env must be either 'local' or 'ci'"
     exit 1
diff --git a/test/shell/test_scalafmt_helper.sh b/test/shell/test_scalafmt_helper.sh
index ca7302421..50414f991 100755
--- a/test/shell/test_scalafmt_helper.sh
+++ b/test/shell/test_scalafmt_helper.sh
@@ -1,57 +1,60 @@
 backup_unformatted() {
-  FILE_PATH=$1
-  FILENAME=$2
-  cp $FILE_PATH/unformatted/unformatted-$FILENAME.scala $FILE_PATH/unformatted/unformatted-$FILENAME.backup.scala
+  local FILE_PATH="$1"
+  local FILENAME="$2"
+  cp "$FILE_PATH/unformatted/unformatted-$FILENAME.scala" \
+    "$FILE_PATH/unformatted/unformatted-$FILENAME.backup.scala"
 }
 
 restore_unformatted_before_exit() {
-  FILE_PATH=$1
-  FILENAME=$2
-  cp $FILE_PATH/unformatted/unformatted-$FILENAME.backup.scala $FILE_PATH/unformatted/unformatted-$FILENAME.scala
-  rm -f $FILE_PATH/unformatted/unformatted-$FILENAME.backup.scala
+  local FILE_PATH="$1"
+  local FILENAME="$2"
+  cp "$FILE_PATH/unformatted/unformatted-$FILENAME.backup.scala" \
+    "$FILE_PATH/unformatted/unformatted-$FILENAME.scala"
+  rm -f "$FILE_PATH/unformatted/unformatted-$FILENAME.backup.scala"
 }
 
 run_formatting() {
   set +e
 
-  PACKAGE_DIR=$1
-  RULE_TYPE=$2
-  FILENAME=$3
+  local PACKAGE_DIR="$1"
+  local RULE_TYPE="$2"
+  local FILENAME="$3"
 
   #on windows scalafmt targets need to be run using bash. 
   #TODO: improve the scalafmt funcitonality so we don't need to use the run_under mechanism
-  local run_under=""
+  local bazel_run=('bazel' 'run')
   if is_windows; then
-    run_under="--run_under=bash"
+    bazel_run+=('--run_under=bash')
   fi
 
-  bazel run //$PACKAGE_DIR:formatted-$RULE_TYPE.format-test $run_under
+  "${bazel_run[@]}" "//$PACKAGE_DIR:formatted-$RULE_TYPE.format-test"
   if [ $? -ne 0 ]; then
     echo -e "${RED} formatted-$RULE_TYPE.format-test should be a formatted target. $NC"
     exit 1
   fi
 
-  bazel run //$PACKAGE_DIR:unformatted-$RULE_TYPE.format-test $run_under
+  "${bazel_run[@]}" "//$PACKAGE_DIR:unformatted-$RULE_TYPE.format-test"
   if [ $? -eq 0 ]; then
     echo -e "${RED} unformatted-$RULE_TYPE.format-test should be an unformatted target. $NC"
     exit 1
   fi
 
-  backup_unformatted $PACKAGE_DIR $FILENAME
+  backup_unformatted "$PACKAGE_DIR" "$FILENAME"
   # format unformatted*.scala
 
-  bazel run //$PACKAGE_DIR:unformatted-$RULE_TYPE.format $run_under
+  "${bazel_run[@]}" "//$PACKAGE_DIR:unformatted-$RULE_TYPE.format"
   if [ $? -ne 0 ]; then
     echo -e "${RED} unformatted-$RULE_TYPE.format should run formatting. $NC"
-    restore_unformatted_before_exit $PACKAGE_DIR $FILENAME
+    restore_unformatted_before_exit "$PACKAGE_DIR" "$FILENAME"
     exit 1
   fi
 
-  diff $FILE_PATH/unformatted/unformatted-$FILENAME.scala $FILE_PATH/formatted/formatted-$FILENAME.scala
+  diff "$PACKAGE_DIR/unformatted/unformatted-$FILENAME.scala" \
+    "$PACKAGE_DIR/formatted/formatted-$FILENAME.scala"
   if [ $? -ne 0 ]; then
     echo -e "${RED} unformatted-$FILENAME.scala should be the same as formatted-$FILENAME.scala after formatting. $NC"
-    restore_unformatted_before_exit $PACKAGE_DIR $FILENAME
+    restore_unformatted_before_exit "$PACKAGE_DIR" "$FILENAME"
     exit 1
   fi
-  restore_unformatted_before_exit $FILE_PATH $FILENAME
+  restore_unformatted_before_exit "$PACKAGE_DIR" "$FILENAME"
 }