diff --git a/tests/androidmk_test.sh b/tests/androidmk_test.sh
index 331dc77..d0d382b 100755
--- a/tests/androidmk_test.sh
+++ b/tests/androidmk_test.sh
@@ -5,7 +5,7 @@
 # How to run: bash path-to-script/androidmk_test.sh
 # Tests of converting license functionality of the androidmk tool
 REAL_TOP="$(readlink -f "$(dirname "$0")"/../../..)"
-$REAL_TOP/build/soong/soong_ui.bash --make-mode androidmk
+"$REAL_TOP/build/soong/soong_ui.bash" --make-mode androidmk
 
 source "$(dirname "$0")/lib.sh"
 
@@ -113,11 +113,14 @@
   run_androidmk_test "a/b/c/d/Android.mk" "a/b/c/d/Android.bp"
 }
 
-run_androidmk_test () {
+function run_androidmk_test {
   export ANDROID_BUILD_TOP="$MOCK_TOP"
-
-  local out=$($REAL_TOP/*/host/*/bin/androidmk "$1")
-  local expected=$(<"$2")
+  local -r androidmk=("$REAL_TOP"/*/host/*/bin/androidmk)
+  if [[ ${#androidmk[@]} -ne 1 ]]; then
+    fail "Multiple androidmk binaries found: ${androidmk[*]}"
+  fi
+  local -r out=$("${androidmk[0]}" "$1")
+  local -r expected=$(<"$2")
 
   if [[ "$out" != "$expected" ]]; then
     ANDROID_BUILD_TOP="$REAL_TOP"
diff --git a/tests/bp2build_bazel_test.sh b/tests/bp2build_bazel_test.sh
index 78ddced..3cdf6aa 100755
--- a/tests/bp2build_bazel_test.sh
+++ b/tests/bp2build_bazel_test.sh
@@ -11,10 +11,10 @@
 function test_bp2build_null_build() {
   setup
   run_soong bp2build
-  local output_mtime1=$(stat -c "%y" out/soong/bp2build_workspace_marker)
+  local -r output_mtime1=$(stat -c "%y" out/soong/bp2build_workspace_marker)
 
   run_soong bp2build
-  local output_mtime2=$(stat -c "%y" out/soong/bp2build_workspace_marker)
+  local -r output_mtime2=$(stat -c "%y" out/soong/bp2build_workspace_marker)
 
   if [[ "$output_mtime1" != "$output_mtime2" ]]; then
     fail "Output bp2build marker file changed on null build"
@@ -36,10 +36,10 @@
   touch foo/bar/a.txt foo/bar/b.txt
 
   run_soong bp2build
-  local output_mtime1=$(stat -c "%y" out/soong/bp2build_workspace_marker)
+  local -r output_mtime1=$(stat -c "%y" out/soong/bp2build_workspace_marker)
 
   run_soong bp2build
-  local output_mtime2=$(stat -c "%y" out/soong/bp2build_workspace_marker)
+  local -r output_mtime2=$(stat -c "%y" out/soong/bp2build_workspace_marker)
 
   if [[ "$output_mtime1" != "$output_mtime2" ]]; then
     fail "Output bp2build marker file changed on null build"
@@ -147,10 +147,10 @@
   run_soong bp2build
 
   run_bazel build --package_path=out/soong/workspace //a:qq
-  local output_mtime1=$(stat -c "%y" bazel-bin/a/_objs/qq/qq.o)
+  local -r output_mtime1=$(stat -c "%y" bazel-bin/a/_objs/qq/qq.o)
 
   run_bazel build --package_path=out/soong/workspace //a:qq
-  local output_mtime2=$(stat -c "%y" bazel-bin/a/_objs/qq/qq.o)
+  local -r output_mtime2=$(stat -c "%y" bazel-bin/a/_objs/qq/qq.o)
 
   if [[ "$output_mtime1" != "$output_mtime2" ]]; then
     fail "output changed on null build"
@@ -161,7 +161,7 @@
 EOF
 
   run_bazel build --package_path=out/soong/workspace //a:qq
-  local output_mtime3=$(stat -c "%y" bazel-bin/a/_objs/qq/qq.o)
+  local -r output_mtime3=$(stat -c "%y" bazel-bin/a/_objs/qq/qq.o)
 
   if [[ "$output_mtime1" == "$output_mtime3" ]]; then
     fail "output not changed when included header changed"
diff --git a/tests/lib.sh b/tests/lib.sh
index abe84d3..0c78cdf 100644
--- a/tests/lib.sh
+++ b/tests/lib.sh
@@ -8,7 +8,7 @@
 
 REAL_TOP="$(readlink -f "$(dirname "$0")"/../../..)"
 
-if [[ ! -z "$HARDWIRED_MOCK_TOP" ]]; then
+if [[ -n "$HARDWIRED_MOCK_TOP" ]]; then
   MOCK_TOP="$HARDWIRED_MOCK_TOP"
 else
   MOCK_TOP=$(mktemp -t -d st.XXXXX)
@@ -36,37 +36,38 @@
 }
 
 function info {
-  echo -e "\e[92;1m[TEST HARNESS INFO]\e[0m" $*
+  echo -e "\e[92;1m[TEST HARNESS INFO]\e[0m" "$*"
 }
 
 function fail {
-  echo -e "\e[91;1mFAILED:\e[0m" $*
+  echo -e "\e[91;1mFAILED:\e[0m" "$*"
   exit 1
 }
 
-function copy_directory() {
+function copy_directory {
   local dir="$1"
-  local parent="$(dirname "$dir")"
+  local -r parent="$(dirname "$dir")"
 
   mkdir -p "$MOCK_TOP/$parent"
   cp -R "$REAL_TOP/$dir" "$MOCK_TOP/$parent"
 }
 
-function symlink_file() {
+function symlink_file {
   local file="$1"
 
   mkdir -p "$MOCK_TOP/$(dirname "$file")"
   ln -s "$REAL_TOP/$file" "$MOCK_TOP/$file"
 }
 
-function symlink_directory() {
+function symlink_directory {
   local dir="$1"
 
   mkdir -p "$MOCK_TOP/$dir"
   # We need to symlink the contents of the directory individually instead of
   # using one symlink for the whole directory because finder.go doesn't follow
   # symlinks when looking for Android.bp files
-  for i in $(ls "$REAL_TOP/$dir"); do
+  for i in "$REAL_TOP/$dir"/*; do
+    i=$(basename "$i")
     local target="$MOCK_TOP/$dir/$i"
     local source="$REAL_TOP/$dir/$i"
 
@@ -96,7 +97,7 @@
   touch "$MOCK_TOP/Android.bp"
 }
 
-function setup() {
+function setup {
   cleanup_mock_top
   mkdir -p "$MOCK_TOP"
 
@@ -108,11 +109,12 @@
   tar xzf "$WARMED_UP_MOCK_TOP"
 }
 
-function run_soong() {
+# shellcheck disable=SC2120
+function run_soong {
   build/soong/soong_ui.bash --make-mode --skip-ninja --skip-config --soong-only --skip-soong-tests "$@"
 }
 
-function create_mock_bazel() {
+function create_mock_bazel {
   copy_directory build/bazel
 
   symlink_directory prebuilts/bazel
@@ -126,7 +128,7 @@
   symlink_file tools/bazel
 }
 
-run_bazel() {
+function run_bazel {
   # Remove the ninja_build output marker file to communicate to buildbot that this is not a regular Ninja build, and its
   # output should not be parsed as such.
   rm -rf out/ninja_build
@@ -134,11 +136,11 @@
   tools/bazel "$@"
 }
 
-run_ninja() {
+function run_ninja {
   build/soong/soong_ui.bash --make-mode --skip-config --soong-only --skip-soong-tests "$@"
 }
 
-info "Starting Soong integration test suite $(basename $0)"
+info "Starting Soong integration test suite $(basename "$0")"
 info "Mock top: $MOCK_TOP"