diff --git a/tests/genrule_sandbox_test.py b/tests/genrule_sandbox_test.py
index a9f0c9b..0cebc2a 100755
--- a/tests/genrule_sandbox_test.py
+++ b/tests/genrule_sandbox_test.py
@@ -17,34 +17,37 @@
 import argparse
 import collections
 import json
-import os.path
+import os
 import subprocess
+import sys
 import tempfile
 
-SRC_ROOT_DIR = os.path.abspath(__file__ + "/../../../..")
+def get_top() -> str:
+  path = '.'
+  while not os.path.isfile(os.path.join(path, 'build/soong/tests/genrule_sandbox_test.py')):
+    if os.path.abspath(path) == '/':
+      sys.exit('Could not find android source tree root.')
+    path = os.path.join(path, '..')
+  return os.path.abspath(path)
 
-
-def _module_graph_path(out_dir):
-  return os.path.join(SRC_ROOT_DIR, out_dir, "soong", "module-actions.json")
-
-
-def _build_with_soong(targets, target_product, out_dir, extra_env={}):
+def _build_with_soong(targets, target_product, *, keep_going = False, extra_env={}):
   env = {
+      **os.environ,
       "TARGET_PRODUCT": target_product,
       "TARGET_BUILD_VARIANT": "userdebug",
   }
-  env.update(os.environ)
   env.update(extra_env)
   args = [
       "build/soong/soong_ui.bash",
       "--make-mode",
       "--skip-soong-tests",
   ]
+  if keep_going:
+    args.append("-k")
   args.extend(targets)
   try:
-    out = subprocess.check_output(
+    subprocess.check_output(
         args,
-        cwd=SRC_ROOT_DIR,
         env=env,
     )
   except subprocess.CalledProcessError as e:
@@ -55,14 +58,13 @@
 
 
 def _find_outputs_for_modules(modules, out_dir, target_product):
-  module_path = os.path.join(
-      SRC_ROOT_DIR, out_dir, "soong", "module-actions.json"
-  )
+  module_path = os.path.join(out_dir, "soong", "module-actions.json")
 
   if not os.path.exists(module_path):
-    _build_with_soong(["json-module-graph"], target_product, out_dir)
+    _build_with_soong(["json-module-graph"], target_product)
 
-  action_graph = json.load(open(_module_graph_path(out_dir)))
+  with open(module_path) as f:
+    action_graph = json.load(f)
 
   module_to_outs = collections.defaultdict(set)
   for mod in action_graph:
@@ -74,50 +76,15 @@
   return module_to_outs
 
 
-def _store_outputs_to_tmp(output_files):
-  try:
-    tempdir = tempfile.TemporaryDirectory()
-    for f in output_files:
-      out = subprocess.check_output(
-          ["cp", "--parents", f, tempdir.name],
-          cwd=SRC_ROOT_DIR,
-      )
-    return tempdir
-  except subprocess.CalledProcessError as e:
-    print(e)
-    print(e.stdout)
-    print(e.stderr)
-
-
-def _diff_outs(file1, file2, show_diff):
-  output = None
-  base_args = ["diff"]
-  if not show_diff:
-    base_args.append("--brief")
-  try:
-    args = base_args + [file1, file2]
-    output = subprocess.check_output(
-        args,
-        cwd=SRC_ROOT_DIR,
-    )
-  except subprocess.CalledProcessError as e:
-    if e.returncode == 1:
-      if show_diff:
-        return output
-      return True
-  return None
-
-
-def _compare_outputs(module_to_outs, tempdir, show_diff):
+def _compare_outputs(module_to_outs, tempdir) -> dict[str, list[str]]:
   different_modules = collections.defaultdict(list)
   for module, outs in module_to_outs.items():
     for out in outs:
-      output = None
-      diff = _diff_outs(os.path.join(tempdir.name, out), out, show_diff)
-      if diff:
-        different_modules[module].append(diff)
+      try:
+        subprocess.check_output(["diff", os.path.join(tempdir, out), out])
+      except subprocess.CalledProcessError as e:
+        different_modules[module].append(e.stdout)
 
-  tempdir.cleanup()
   return different_modules
 
 
@@ -138,53 +105,56 @@
       "--show-diff",
       "-d",
       action="store_true",
-      required=False,
       help="whether to display differing files",
   )
   parser.add_argument(
       "--output-paths-only",
       "-o",
       action="store_true",
-      required=False,
       help="Whether to only return the output paths per module",
   )
   args = parser.parse_args()
+  os.chdir(get_top())
 
   out_dir = os.environ.get("OUT_DIR", "out")
-  target_product = args.target_product
-  modules = set(args.modules)
 
-  module_to_outs = _find_outputs_for_modules(modules, out_dir, target_product)
+  print("finding output files for the modules...")
+  module_to_outs = _find_outputs_for_modules(set(args.modules), out_dir, args.target_product)
   if not module_to_outs:
-    print("No outputs found")
-    exit(1)
+    sys.exit("No outputs found")
 
   if args.output_paths_only:
     for m, o in module_to_outs.items():
       print(f"{m} outputs: {o}")
-    exit(0)
+    sys.exit(0)
 
-  all_outs = set()
-  for outs in module_to_outs.values():
-    all_outs.update(outs)
-  print("build without sandboxing")
-  _build_with_soong(list(all_outs), target_product, out_dir)
-  tempdir = _store_outputs_to_tmp(all_outs)
-  print("build with sandboxing")
-  _build_with_soong(
-      list(all_outs),
-      target_product,
-      out_dir,
-      extra_env={"GENRULE_SANDBOXING": "true"},
-  )
-  diffs = _compare_outputs(module_to_outs, tempdir, args.show_diff)
-  if len(diffs) == 0:
-    print("All modules are correct")
-  elif args.show_diff:
-    for m, d in diffs.items():
-      print(f"Module {m} has diffs {d}")
-  else:
-    print(f"Modules {list(diffs.keys())} have diffs")
+  all_outs = list(set.union(*module_to_outs.values()))
+
+  print("building without sandboxing...")
+  _build_with_soong(all_outs, args.target_product)
+  with tempfile.TemporaryDirectory() as tempdir:
+    for f in all_outs:
+      subprocess.check_call(["cp", "--parents", f, tempdir])
+
+    print("building with sandboxing...")
+    _build_with_soong(
+        all_outs,
+        args.target_product,
+        # We've verified these build without sandboxing already, so do the sandboxing build
+        # with keep_going = True so that we can find all the genrules that fail to build with
+        # sandboxing.
+        keep_going = True,
+        extra_env={"GENRULE_SANDBOXING": "true"},
+    )
+
+    diffs = _compare_outputs(module_to_outs, tempdir)
+    if len(diffs) == 0:
+      print("All modules are correct")
+    elif args.show_diff:
+      for m, d in diffs.items():
+        print(f"Module {m} has diffs {d}")
+    else:
+      print(f"Modules {list(diffs.keys())} have diffs")
 
 
 if __name__ == "__main__":