Add unit test for --version

tests/test_cli.py

@@ -3,6 +3,7 @@
 import contextlib
 import copy
 import os
+import re
 import shutil
 import sys
 import tempfile
@@ -163,6 +164,17 @@ def test_display_banner(self, capfd) -> None:  # type: ignore[no-untyped-def]
         for line in plain_lines:
             assert len(line) == banner_width, "banner has inconsistent width"
 
+    def test_version(self) -> None:
+        result = self.run_cli("--version")
+        result.assert_success()
+
+        with open("share/version.txt") as f:
+            valid_version_regex = r"\d+\.\d+\.\d+"
+            version = f.read().strip()
+
+            assert re.match(valid_version_regex, version)
+            assert version in result.stdout
+
 
 class TestCliConversion(TestCliBasic):
     def test_invalid_lang(self) -> None: