rust: Add test for bootstrapped rust install with C.DEFAULT

tests/languages/rust_test.py

@@ -33,7 +33,8 @@ def test_uses_default_when_rust_is_not_available(cmd_output_b_mck):
     assert ACTUAL_GET_DEFAULT_VERSION() == C.DEFAULT
 
 
-def test_installs_with_bootstrapped_rustup(tmpdir):
+@pytest.mark.parametrize('language_version', (C.DEFAULT, '1.56.0'))
+def test_installs_with_bootstrapped_rustup(tmpdir, language_version):
     tmpdir.join('src', 'main.rs').ensure().write(
         'fn main() {'
         '    println!("Hello, world!");'
@@ -68,13 +69,13 @@ def mocked_find_executable(exe: str) -> str | None:
 
     with mock.patch.object(parse_shebang, 'find_executable') as find_exe_mck:
         find_exe_mck.side_effect = mocked_find_executable
-        rust.install_environment(prefix, '1.64.0', ())
+        rust.install_environment(prefix, language_version, ())
         assert find_executable_exes == ['rustup', 'rustup', 'cargo']
 
     # this directory shouldn't exist, make sure we succeed without it existing
     shutil.rmtree(tmpdir.join('target'))
 
-    with rust.in_env(prefix, '1.64.0'):
+    with rust.in_env(prefix, language_version):
         assert cmd_output('hello_world')[1] == 'Hello, world!\n'