Add basic test to ensure LSP can start and stop (#275)

Author: amyreese

ufmt/tests/__init__.py

@@ -4,4 +4,5 @@
 from .cli import CliTest
 from .config import ConfigTest
 from .core import CoreTest
+from .lsp import LspTest
 from .util import UtilTest

ufmt/tests/lsp.py

@@ -0,0 +1,32 @@
+# Copyright Amethyst Reese
+# Licensed under the MIT license
+
+from io import StringIO
+from pathlib import Path
+from tempfile import TemporaryDirectory
+from threading import Timer
+from unittest import TestCase
+
+from ufmt.lsp import ufmt_lsp
+
+
+class LspTest(TestCase):
+    def setUp(self) -> None:
+        self.td = TemporaryDirectory()
+        self.tdp = Path(self.td.name).resolve()
+        self.addCleanup(self.td.cleanup)
+
+    def test_startup_shutdown(self) -> None:
+        stdin = StringIO()
+        stdout = StringIO()
+
+        server = ufmt_lsp(root=self.tdp)
+
+        def times_up() -> None:
+            server.shutdown()  # type:ignore[no-untyped-call]
+            raise RuntimeError("had to forcefully shutdown lsp")
+
+        timer = Timer(5, times_up)
+        timer.start()
+        server.start_io(stdin, stdout)
+        timer.cancel()