test docker and docker_image directly

tests/languages/docker_image_test.py

@@ -0,0 +1,27 @@
+from __future__ import annotations
+
+from pre_commit.languages import docker_image
+from testing.language_helpers import run_language
+from testing.util import xfailif_windows
+
+
+@xfailif_windows  # pragma: win32 no cover
+def test_docker_image_hook_via_entrypoint(tmp_path):
+    ret = run_language(
+        tmp_path,
+        docker_image,
+        '--entrypoint echo ubuntu:22.04',
+        args=('hello hello world',),
+    )
+    assert ret == (0, b'hello hello world\n')
+
+
+@xfailif_windows  # pragma: win32 no cover
+def test_docker_image_hook_via_args(tmp_path):
+    ret = run_language(
+        tmp_path,
+        docker_image,
+        'ubuntu:22.04 echo',
+        args=('hello hello world',),
+    )
+    assert ret == (0, b'hello hello world\n')