test: add test for cargo provider with lock files

Add a test to check the behavior of the cargo provider when a
`Cargo.lock` file is present. This test ensures that the
`CargoProvider` behaves correctly when the lock file is present, and
updates both the `Cargo.lock` and `Cargo.toml` files accordingly.

Author: tunakasif

tests/providers/test_cargo_provider.py

@@ -33,6 +33,32 @@
 version = "42.1"
 """
 
+CARGO_LOCK = """\
+[[package]]
+name = "whatever"
+version = "0.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "123abc"
+dependencies = [
+ "packageA",
+ "packageB",
+ "packageC",
+]
+"""
+
+CARGO_LOCK_EXPECTED = """\
+[[package]]
+name = "whatever"
+version = "42.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "123abc"
+dependencies = [
+ "packageA",
+ "packageB",
+ "packageC",
+]
+"""
+
 
 @pytest.mark.parametrize(
     "content, expected",
@@ -58,3 +84,46 @@ def test_cargo_provider(
 
     provider.set_version("42.1")
     assert file.read_text() == dedent(expected)
+
+
+@pytest.mark.parametrize(
+    "toml_content, lock_content, toml_expected, lock_expected",
+    (
+        (
+            CARGO_TOML,
+            CARGO_LOCK,
+            CARGO_TOML_EXPECTED,
+            CARGO_LOCK_EXPECTED,
+        ),
+        (
+            CARGO_WORKSPACE_TOML,
+            CARGO_LOCK,
+            CARGO_WORKSPACE_TOML_EXPECTED,
+            CARGO_LOCK_EXPECTED,
+        ),
+    ),
+)
+def test_cargo_provider_with_lock(
+    config: BaseConfig,
+    chdir: Path,
+    toml_content: str,
+    lock_content: str,
+    toml_expected: str,
+    lock_expected: str,
+):
+    filename = CargoProvider.filename
+    file = chdir / filename
+    file.write_text(dedent(toml_content))
+
+    lock_filename = CargoProvider.lock_filename
+    lock_file = chdir / lock_filename
+    lock_file.write_text(dedent(lock_content))
+    config.settings["version_provider"] = "cargo"
+
+    provider = get_provider(config)
+    assert isinstance(provider, CargoProvider)
+    assert provider.get_version() == "0.1.0"
+
+    provider.set_version("42.1")
+    assert file.read_text() == dedent(toml_expected)
+    assert lock_file.read_text() == dedent(lock_expected)