Add tests for select_config_file

tests/conftest.py

@@ -454,13 +454,14 @@ def make_config_file(tmpdir_cwd):
     def _maker(
         pyproject_param: str, new_default: Any, config_file_name: str = CONFIG_FILE_NAME
     ) -> Path:
-        # Make a config file with this one config default override
-        config_path = Path(tmpdir_cwd) / pyproject_param
-        config_file = config_path / config_file_name
-        config_path.mkdir(exist_ok=True)
+        # Create a nested directory structure if config_file_name includes directories
+        config_dir = Path(tmpdir_cwd / config_file_name).parent
+        config_dir.mkdir(exist_ok=True, parents=True)
 
+        # Make a config file with this one config default override
+        config_file = Path(tmpdir_cwd / config_file_name)
         config_to_dump = {"tool": {"pip-tools": {pyproject_param: new_default}}}
-        config_file.write_text(tomli_w.dumps(config_to_dump))
+        config_file.write_text(tomli_w.dumps(config_to_dump), encoding="utf-8")
         return config_file.relative_to(tmpdir_cwd)
 
     return _maker

tests/test_utils.py

@@ -6,6 +6,7 @@
 import shlex
 import sys
 from pathlib import Path
+from textwrap import dedent
 
 import pip
 import pytest
@@ -31,6 +32,7 @@
     lookup_table,
     lookup_table_from_tuples,
     override_defaults_from_config_file,
+    select_config_file,
 )
 
 
@@ -708,3 +710,52 @@ def test_callback_config_file_defaults_unreadable_toml(make_config_file):
             "config",
             "/dev/null/path/does/not/exist/my-config.toml",
         )
+
+
+def test_select_config_file_no_files(tmpdir_cwd):
+    assert select_config_file(()) is None
+
+
+@pytest.mark.parametrize("filename", ("pyproject.toml", ".pip-tools.toml"))
+def test_select_config_file_returns_config_in_cwd(make_config_file, filename):
+    config_file = make_config_file("dry-run", True, filename)
+    assert select_config_file(()) == config_file
+
+
+def test_select_config_file_returns_empty_config_file_in_cwd(tmpdir_cwd):
+    config_file = Path(".pip-tools.toml")
+    config_file.touch()
+
+    assert select_config_file(()) == config_file
+
+
+def test_select_config_file_cannot_find_config_in_cwd(tmpdir_cwd, make_config_file):
+    make_config_file("dry-run", True, "subdir/pyproject.toml")
+    assert select_config_file(()) is None
+
+
+def test_select_config_file_with_config_file_in_subdir(tmpdir_cwd, make_config_file):
+    config_file = make_config_file("dry-run", True, "subdir/.pip-tools.toml")
+
+    requirement_file = Path("subdir/requirements.in")
+    requirement_file.touch()
+
+    assert select_config_file((requirement_file.as_posix(),)) == config_file
+
+
+def test_select_config_file_prefers_pip_tools_toml_over_pyproject_toml(tmpdir_cwd):
+    pip_tools_file = Path(".pip-tools.toml")
+    pip_tools_file.touch()
+
+    pyproject_file = Path("pyproject.toml")
+    pyproject_file.write_text(
+        dedent(
+            """\
+        [build-system]
+        requires = ["setuptools>=63", "setuptools_scm[toml]>=7"]
+        build-backend = "setuptools.build_meta"
+        """
+        )
+    )
+
+    assert select_config_file(()) == pip_tools_file