diff --git a/pyperformance/_pyproject_toml.py b/pyperformance/_pyproject_toml.py
index 323fb6aa..40b26e82 100644
--- a/pyperformance/_pyproject_toml.py
+++ b/pyperformance/_pyproject_toml.py
@@ -175,7 +175,7 @@ def _normalize_project(data, rootdir, name, requirefiles, **_ignored):
     key = "readme"
     if key in data:
         readme = data[key]
-        if isinstance(readme, "str"):
+        if isinstance(readme, str):
             readme = data[key] = {"file": readme}
         # XXX Check the suffix.
         # XXX Handle 'content-type'.
diff --git a/pyperformance/tests/test_pyproject_toml.py b/pyperformance/tests/test_pyproject_toml.py
new file mode 100644
index 00000000..022dd4aa
--- /dev/null
+++ b/pyperformance/tests/test_pyproject_toml.py
@@ -0,0 +1,99 @@
+import pathlib
+import tempfile
+import unittest
+
+from pyperformance import _pyproject_toml
+
+
+class TestPyProjectToml(unittest.TestCase):
+    def test_parse_project_with_readme_string(self):
+        with tempfile.TemporaryDirectory() as tmpdir:
+            tmp_path = pathlib.Path(tmpdir)
+            toml_content = """
+            [project]
+            name = "my-test-bench"
+            version = "1.0"
+            readme = "README.md"
+            """
+            (tmp_path / "README.md").touch()
+
+            data = _pyproject_toml.parse_pyproject_toml(
+                toml_content, rootdir=str(tmp_path), requirefiles=True
+            )
+            self.assertEqual(data["project"]["readme"]["file"], "README.md")
+
+    def test_parse_full_valid_project_section(self):
+        with tempfile.TemporaryDirectory() as tmpdir:
+            toml_content = """
+            [project]
+            name = "my-full-bench"
+            version = "2.1.3"
+            dependencies = [
+                "pyperf",
+                "six",
+            ]
+            requires-python = ">=3.12"
+            """
+            data = _pyproject_toml.parse_pyproject_toml(
+                toml_content, rootdir=str(tmpdir)
+            )
+            project = data["project"]
+            self.assertEqual(project["name"], "my-full-bench")
+            self.assertEqual(project["version"], "2.1.3")
+            self.assertEqual(project["dependencies"], ["pyperf", "six"])
+            self.assertEqual(project["requires-python"], ">=3.12")
+
+    def test_parse_fails_on_missing_name(self):
+        with tempfile.TemporaryDirectory() as tmpdir:
+            toml_content = """
+            [project]
+            version = "1.0"
+            """
+
+            with self.assertRaisesRegex(ValueError, r'missing required "name" field'):
+                _pyproject_toml.parse_pyproject_toml(toml_content, rootdir=str(tmpdir))
+
+    def test_parse_fails_on_unsupported_section(self):
+        with tempfile.TemporaryDirectory() as tmpdir:
+            toml_content = """
+            [project]
+            name = "my-test-bench"
+            version = "1.0"
+
+            [foobar]
+            key = "value"
+            """
+
+            with self.assertRaisesRegex(ValueError, "unsupported sections"):
+                _pyproject_toml.parse_pyproject_toml(toml_content, rootdir=str(tmpdir))
+
+    def test_parse_readme_file_missing_with_requirefiles_true(self):
+        with tempfile.TemporaryDirectory() as tmpdir:
+            toml_content = """
+            [project]
+            name = "my-test-bench"
+            version = "1.0"
+            readme = "MISSING_README.md"
+            """
+
+            with self.assertRaisesRegex(ValueError, "does not exist"):
+                _pyproject_toml.parse_pyproject_toml(
+                    toml_content, rootdir=str(tmpdir), requirefiles=True
+                )
+
+    def test_parse_readme_file_missing_with_requirefiles_false(self):
+        with tempfile.TemporaryDirectory() as tmpdir:
+            toml_content = """
+            [project]
+            name = "my-test-bench"
+            version = "1.0"
+            readme = "MISSING_README.md"
+            """
+            data = _pyproject_toml.parse_pyproject_toml(
+                toml_content, rootdir=str(tmpdir), requirefiles=False
+            )
+            self.assertEqual(data["project"]["readme"]["file"], "MISSING_README.md")
+
+
+if __name__ == "__main__":
+    unittest.main()