test swift language directly

tests/languages/swift_test.py

@@ -0,0 +1,31 @@
+from __future__ import annotations
+
+import sys
+
+import pytest
+
+from pre_commit.languages import swift
+from testing.language_helpers import run_language
+
+
+@pytest.mark.skipif(
+    sys.platform == 'win32',
+    reason='swift is not supported on windows',
+)
+def test_swift_language(tmp_path):  # pragma: win32 no cover
+    package_swift = '''\
+// swift-tools-version:5.0
+import PackageDescription
+
+let package = Package(
+    name: "swift_hooks_repo",
+    targets: [.target(name: "swift_hooks_repo")]
+)
+'''
+    tmp_path.joinpath('Package.swift').write_text(package_swift)
+    src_dir = tmp_path.joinpath('Sources/swift_hooks_repo')
+    src_dir.mkdir(parents=True)
+    src_dir.joinpath('main.swift').write_text('print("Hello, world!")\n')
+
+    expected = (0, b'Hello, world!\n')
+    assert run_language(tmp_path, swift, 'swift_hooks_repo') == expected