@@ -15,7 +15,7 @@ def find_leading_whitespace(s):
     match = re.match(r"(\s+)", s)
     if match:
         return match.group(1)
-    return ""
+    return ""  # pragma: no cover
 
 
 def added_line_nums_strategy(lines, i):
@@ -79,7 +79,7 @@ def build_new_lines(
         configparser does not retain formatting or comment lines, so we have to build
         the output newline manually.
         """
-        clean_lines = list(map(lambda s: s.strip(), original_lines))
+        clean_lines = [s.strip() for s in original_lines]
 
         newline_separated = len(defined_dependencies.split("\n")) > 1
         if newline_separated:
 
@@ -20,7 +20,7 @@ def _parse_file(self, file: Path) -> PackageStore | None:
             config.read(file)
         except configparser.ParsingError:
             logger.debug("Unable to parse setup.cfg file.")
-            return None
+            return None  # pragma: no cover
 
         if "options" not in config:
             return None
 
@@ -79,3 +79,25 @@ def pkg_with_reqs_txt_unknown_encoding(tmp_path_factory):
     reqs = "\xf0\x28\x8c\xbc"
     req_file.write_text(reqs)
     return base_dir
+
+
+@pytest.fixture(scope="module")
+def pkg_with_setup_cfg(tmp_path_factory):
+    base_dir = tmp_path_factory.mktemp("foo")
+    req_file = base_dir / "setup.cfg"
+    reqs = """\
+        [metadata]
+        name = my_package
+        version = attr: my_package.VERSION
+
+        # some other stuff
+
+        [options]
+        include_package_data = True
+        python_requires = >=3.7
+        install_requires =
+            requests
+            importlib-metadata; python_version<"3.8"
+    """
+    req_file.write_text(reqs)
+    return base_dir
@@ -3,7 +3,10 @@
 from codemodder.change import ChangeSet
 from codemodder.dependency import DefusedXML, Security
 from codemodder.dependency_management import DependencyManager
-from codemodder.project_analysis.file_parsers import RequirementsTxtParser
+from codemodder.project_analysis.file_parsers import (
+    RequirementsTxtParser,
+    SetupCfgParser,
+)
 from codemodder.project_analysis.file_parsers.package_store import PackageStore
 
 
@@ -33,3 +36,15 @@ def test_write_for_requirements_txt(self, pkg_with_reqs_txt):
 
         changeset = dm.write(dependencies)
         assert isinstance(changeset, ChangeSet)
+        assert len(changeset.changes)
+
+    def test_write_for_setup_cfg(self, pkg_with_setup_cfg):
+        parser = SetupCfgParser(pkg_with_setup_cfg)
+        stores = parser.parse()
+        assert len(stores) == 1
+        dm = DependencyManager(stores[0], pkg_with_setup_cfg)
+        dependencies = [DefusedXML, Security]
+
+        changeset = dm.write(dependencies)
+        assert isinstance(changeset, ChangeSet)
+        assert len(changeset.changes)
@@ -1,4 +1,5 @@
 from textwrap import dedent
+import mock
 import pytest
 
 from codemodder.dependency_management.setupcfg_writer import SetupCfgWriter
@@ -237,6 +238,42 @@ def test_cfg_bad_formatting(tmpdir):
     assert setup_cfg.read() == dedent(orig_setupcfg)
 
 
+@mock.patch(
+    "codemodder.dependency_management.setupcfg_writer.SetupCfgWriter.build_new_lines",
+    return_value=None,
+)
+def test_cfg_cant_build_newlines(_, tmpdir):
+    orig_setupcfg = """\
+        [metadata]
+        name = my_package
+        version = attr: my_package.VERSION
+
+        # some other stuff
+
+        [options]
+        include_package_data = True
+        python_requires = >=3.7
+        install_requires =
+            requests
+            importlib-metadata; python_version<"3.8"
+    """
+
+    setup_cfg = tmpdir.join("setup.cfg")
+    setup_cfg.write(dedent(orig_setupcfg))
+
+    store = PackageStore(
+        type=FileType.SETUP_CFG,
+        file=str(setup_cfg),
+        dependencies=set(),
+        py_versions=[">=3.7"],
+    )
+
+    writer = SetupCfgWriter(store, tmpdir)
+    dependencies = [Security, Security]
+    writer.write(dependencies)
+    assert setup_cfg.read() == dedent(orig_setupcfg)
+
+
 def test_cfg_inline_dependencies(tmpdir):
     orig_setupcfg = """\
         [metadata]