Add more tests for usethis tool ruff (#52)

.pre-commit-config.yaml

@@ -1,6 +1,6 @@
 repos:
   - repo: https://github.com/abravalheri/validate-pyproject
-    rev: "v0.21"
+    rev: "v0.22"
     hooks:
       - id: validate-pyproject
         additional_dependencies: ["validate-pyproject-schema-store[all]"]

src/usethis/_integrations/pre_commit/core.py

@@ -13,7 +13,7 @@
         additional_dependencies: ["validate-pyproject-schema-store[all]"]
 """
 # Manually bump this version when necessary
-_VALIDATEPYPROJECT_VERSION = "v0.21"
+_VALIDATEPYPROJECT_VERSION = "v0.22"
 
 
 def add_pre_commit_config() -> None:

tests/usethis/_interface/test_tool.py

@@ -405,6 +405,38 @@ def test_config_file(self, uv_init_dir: Path):
             # Assert
             assert (uv_init_dir / "pyproject.toml").read_text() == ""
 
+        def test_blank_slate(self, uv_init_dir: Path):
+            # Arrange
+            contents = (uv_init_dir / "pyproject.toml").read_text()
+
+            # Act
+            with change_cwd(uv_init_dir):
+                _ruff(remove=True, offline=is_offline())
+
+            # Assert
+            assert (uv_init_dir / "pyproject.toml").read_text() == contents
+
+        def test_roundtrip(self, uv_init_dir: Path):
+            # Arrange
+            contents = (uv_init_dir / "pyproject.toml").read_text()
+
+            # Act
+            with change_cwd(uv_init_dir):
+                _ruff(offline=is_offline())
+                _ruff(remove=True, offline=is_offline())
+
+            # Assert
+            assert (
+                (uv_init_dir / "pyproject.toml").read_text()
+                == contents
+                + """\
+
+[tool.uv]
+dev-dependencies = []
+
+"""
+            )
+
 
 class TestPytest:
     def test_dep(self, uv_init_dir: Path):