1 files changed, 90 insertions, 0 deletions
diff --git a/tests/languages/rust_test.py b/tests/languages/rust_test.py
new file mode 100644
index 0000000..f011e71
--- /dev/null
+++ b/tests/languages/rust_test.py
@@ -0,0 +1,90 @@
+from __future__ import annotations
+
+from unittest import mock
+
+import pytest
+
+import pre_commit.constants as C
+from pre_commit import parse_shebang
+from pre_commit.languages import rust
+from pre_commit.prefix import Prefix
+from pre_commit.util import cmd_output
+
+ACTUAL_GET_DEFAULT_VERSION = rust.get_default_version.__wrapped__
+
+
+@pytest.fixture
+def cmd_output_b_mck():
+    with mock.patch.object(rust, 'cmd_output_b') as mck:
+        yield mck
+
+
+def test_sets_system_when_rust_is_available(cmd_output_b_mck):
+    cmd_output_b_mck.return_value = (0, b'', b'')
+    assert ACTUAL_GET_DEFAULT_VERSION() == 'system'
+
+
+def test_uses_default_when_rust_is_not_available(cmd_output_b_mck):
+    cmd_output_b_mck.return_value = (127, b'', b'error: not found')
+    assert ACTUAL_GET_DEFAULT_VERSION() == C.DEFAULT
+
+
+@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() {\n'
+        '    println!("Hello, world!");\n'
+        '}\n',
+    )
+    tmpdir.join('Cargo.toml').ensure().write(
+        '[package]\n'
+        'name = "hello_world"\n'
+        'version = "0.1.0"\n'
+        'edition = "2021"\n',
+    )
+    prefix = Prefix(str(tmpdir))
+
+    find_executable_exes = []
+
+    original_find_executable = parse_shebang.find_executable
+
+    def mocked_find_executable(exe: str) -> str | None:
+        """
+        Return `None` the first time `find_executable` is called to ensure
+        that the bootstrapping code is executed, then just let the function
+        work as normal.
+
+        Also log the arguments to ensure that everything works as expected.
+        """
+        find_executable_exes.append(exe)
+        if len(find_executable_exes) == 1:
+            return None
+        return original_find_executable(exe)
+
+    with mock.patch.object(parse_shebang, 'find_executable') as find_exe_mck:
+        find_exe_mck.side_effect = mocked_find_executable
+        rust.install_environment(prefix, language_version, ())
+        assert find_executable_exes == ['rustup', 'rustup', 'cargo']
+
+    with rust.in_env(prefix, language_version):
+        assert cmd_output('hello_world')[1] == 'Hello, world!\n'
+
+
+def test_installs_with_existing_rustup(tmpdir):
+    tmpdir.join('src', 'main.rs').ensure().write(
+        'fn main() {\n'
+        '    println!("Hello, world!");\n'
+        '}\n',
+    )
+    tmpdir.join('Cargo.toml').ensure().write(
+        '[package]\n'
+        'name = "hello_world"\n'
+        'version = "0.1.0"\n'
+        'edition = "2021"\n',
+    )
+    prefix = Prefix(str(tmpdir))
+
+    assert parse_shebang.find_executable('rustup') is not None
+    rust.install_environment(prefix, '1.56.0', ())
+    with rust.in_env(prefix, '1.56.0'):
+        assert cmd_output('hello_world')[1] == 'Hello, world!\n'