diff --git a/pre_commit/util.py b/pre_commit/util.py
index b829a483..dfe07ea9 100644
--- a/pre_commit/util.py
+++ b/pre_commit/util.py
@@ -108,9 +108,9 @@ def _setdefault_kwargs(kwargs: Dict[str, Any]) -> None:
 
 def cmd_output_b(
         *cmd: str,
+        retcode: Optional[int] = 0,
         **kwargs: Any,
 ) -> Tuple[int, bytes, Optional[bytes]]:
-    retcode = kwargs.pop('retcode', 0)
     _setdefault_kwargs(kwargs)
 
     try:
@@ -176,9 +176,10 @@ if os.name != 'nt':  # pragma: windows no cover
 
     def cmd_output_p(
             *cmd: str,
+            retcode: Optional[int] = 0,
             **kwargs: Any,
     ) -> Tuple[int, bytes, Optional[bytes]]:
-        assert kwargs.pop('retcode') is None
+        assert retcode is None
         assert kwargs['stderr'] == subprocess.STDOUT, kwargs['stderr']
         _setdefault_kwargs(kwargs)
 
diff --git a/pre_commit/xargs.py b/pre_commit/xargs.py
index ccd341d4..5235dc65 100644
--- a/pre_commit/xargs.py
+++ b/pre_commit/xargs.py
@@ -117,6 +117,10 @@ def _thread_mapper(maxsize: int) -> Generator[
 def xargs(
         cmd: Tuple[str, ...],
         varargs: Sequence[str],
+        *,
+        color: bool = False,
+        target_concurrency: int = 1,
+        _max_length: int = _get_platform_max_length(),
         **kwargs: Any,
 ) -> Tuple[int, bytes]:
     """A simplified implementation of xargs.
@@ -124,9 +128,6 @@ def xargs(
     color: Make a pty if on a platform that supports it
     target_concurrency: Target number of partitions to run concurrently
     """
-    color = kwargs.pop('color', False)
-    target_concurrency = kwargs.pop('target_concurrency', 1)
-    max_length = kwargs.pop('_max_length', _get_platform_max_length())
     cmd_fn = cmd_output_p if color else cmd_output_b
     retcode = 0
     stdout = b''
@@ -136,7 +137,7 @@ def xargs(
     except parse_shebang.ExecutableNotFoundError as e:
         return e.to_output()[:2]
 
-    partitions = partition(cmd, varargs, target_concurrency, max_length)
+    partitions = partition(cmd, varargs, target_concurrency, _max_length)
 
     def run_cmd_partition(
             run_cmd: Tuple[str, ...],
diff --git a/testing/util.py b/testing/util.py
index dbe475eb..efeb1e01 100644
--- a/testing/util.py
+++ b/testing/util.py
@@ -18,13 +18,15 @@ def get_resource_path(path):
     return os.path.join(TESTING_DIR, 'resources', path)
 
 
-def cmd_output_mocked_pre_commit_home(*args, **kwargs):
-    # keyword-only argument
-    tempdir_factory = kwargs.pop('tempdir_factory')
-    pre_commit_home = kwargs.pop('pre_commit_home', tempdir_factory.get())
+def cmd_output_mocked_pre_commit_home(
+        *args, tempdir_factory, pre_commit_home=None, env=None, **kwargs,
+):
+    if pre_commit_home is None:
+        pre_commit_home = tempdir_factory.get()
+    env = env if env is not None else os.environ
     kwargs.setdefault('stderr', subprocess.STDOUT)
     # Don't want to write to the home directory
-    env = dict(kwargs.pop('env', os.environ), PRE_COMMIT_HOME=pre_commit_home)
+    env = dict(env, PRE_COMMIT_HOME=pre_commit_home)
     ret, out, _ = cmd_output(*args, env=env, **kwargs)
     return ret, out.replace('\r\n', '\n'), None
 
@@ -123,9 +125,7 @@ def cwd(path):
         os.chdir(original_cwd)
 
 
-def git_commit(*args, **kwargs):
-    fn = kwargs.pop('fn', cmd_output)
-    msg = kwargs.pop('msg', 'commit!')
+def git_commit(*args, fn=cmd_output, msg='commit!', **kwargs):
     kwargs.setdefault('stderr', subprocess.STDOUT)
 
     cmd = ('git', 'commit', '--allow-empty', '--no-gpg-sign', '-a') + args
diff --git a/tests/envcontext_test.py b/tests/envcontext_test.py
index 56dd2632..f9d4dce6 100644
--- a/tests/envcontext_test.py
+++ b/tests/envcontext_test.py
@@ -8,12 +8,7 @@ from pre_commit.envcontext import UNSET
 from pre_commit.envcontext import Var
 
 
-def _test(**kwargs):
-    before = kwargs.pop('before')
-    patch = kwargs.pop('patch')
-    expected = kwargs.pop('expected')
-    assert not kwargs
-
+def _test(*, before, patch, expected):
     env = before.copy()
     with envcontext(patch, _env=env):
         assert env == expected