diff --git a/tests/lib.sh b/tests/lib.sh
new file mode 100644
index 0000000..3c97e14
--- /dev/null
+++ b/tests/lib.sh
@@ -0,0 +1,79 @@
+#!/bin/bash -eu
+
+HARDWIRED_MOCK_TOP=
+# Uncomment this to be able to view the source tree after a test is run
+# HARDWIRED_MOCK_TOP=/tmp/td
+
+REAL_TOP="$(readlink -f "$(dirname "$0")"/../../..)"
+
+function fail {
+  echo ERROR: $1
+  exit 1
+}
+
+function copy_directory() {
+  local dir="$1"
+  local parent="$(dirname "$dir")"
+
+  mkdir -p "$MOCK_TOP/$parent"
+  cp -R "$REAL_TOP/$dir" "$MOCK_TOP/$parent"
+}
+
+function symlink_file() {
+  local file="$1"
+
+  mkdir -p "$MOCK_TOP/$(dirname "$file")"
+  ln -s "$REAL_TOP/$file" "$MOCK_TOP/$file"
+}
+
+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/$dir"); do
+    local target="$MOCK_TOP/$dir/$i"
+    local source="$REAL_TOP/$dir/$i"
+
+    if [[ -e "$target" ]]; then
+      if [[ ! -d "$source" || ! -d "$target" ]]; then
+        fail "Trying to symlink $dir twice"
+      fi
+    else
+      ln -s "$REAL_TOP/$dir/$i" "$MOCK_TOP/$dir/$i";
+    fi
+  done
+}
+
+function setup() {
+  if [[ ! -z "$HARDWIRED_MOCK_TOP" ]]; then
+    MOCK_TOP="$HARDWIRED_MOCK_TOP"
+    rm -fr "$MOCK_TOP"
+    mkdir -p "$MOCK_TOP"
+  else
+    MOCK_TOP=$(mktemp -t -d st.XXXXX)
+    trap 'echo cd / && echo rm -fr "$MOCK_TOP"' EXIT
+  fi
+
+  echo "Test case: ${FUNCNAME[1]}, mock top path: $MOCK_TOP"
+  cd "$MOCK_TOP"
+
+  copy_directory build/blueprint
+  copy_directory build/soong
+
+  symlink_directory prebuilts/go
+  symlink_directory prebuilts/build-tools
+  symlink_directory external/golang-protobuf
+
+  touch "$MOCK_TOP/Android.bp"
+
+  export ALLOW_MISSING_DEPENDENCIES=true
+
+  mkdir -p out/soong
+}
+
+function run_soong() {
+  build/soong/soong_ui.bash --make-mode --skip-ninja --skip-make --skip-soong-tests
+}