Add test for tools.setuptools warning

Author: SnoopJ

setuptools/tests/config/test_pyprojecttoml.py

@@ -8,6 +8,7 @@
 from path import Path
 
 from setuptools.config.pyprojecttoml import (
+    _ToolsTypoInMetadata,
     read_configuration,
     expand_configuration,
     apply_configuration,
@@ -369,3 +370,28 @@ def test_include_package_data_in_setuppy(tmp_path):
     assert dist.get_name() == "myproj"
     assert dist.get_version() == "42"
     assert dist.include_package_data is False
+
+
+def test_warn_tools_typo(tmp_path):
+    """Test that the common ``tools.setuptools`` typo in ``pyproject.toml`` issues a warning
+
+    See https://github.com/pypa/setuptools/issues/4150
+    """
+    config = """
+    [build-system]
+    requires = ["setuptools"]
+    build-backend = "setuptools.build_meta"
+
+    [project]
+    name = "myproj"
+    version = '42'
+
+    [tools.setuptools]
+    packages = ["package"]
+    """
+
+    pyproject = tmp_path / "pyproject.toml"
+    pyproject.write_text(cleandoc(config), encoding="utf-8")
+
+    with pytest.warns(_ToolsTypoInMetadata):
+        expanded = read_configuration(pyproject)