From 875df57193b0fde11196c21e4a6e02b4f1a2f2aa Mon Sep 17 00:00:00 2001
From: Matthias Dellweg <mdellweg@redhat.com>
Date: Tue, 7 Nov 2023 12:36:26 +0100
Subject: [PATCH] Refactored test_build.py

Made use of more generic with_[git_]project decorators.
---
 src/towncrier/newsfragments/562.misc |   1 +
 src/towncrier/test/helpers.py        |  71 +-
 src/towncrier/test/test_build.py     | 933 ++++++++++++---------------
 3 files changed, 492 insertions(+), 513 deletions(-)
 create mode 100644 src/towncrier/newsfragments/562.misc

diff --git a/src/towncrier/newsfragments/562.misc b/src/towncrier/newsfragments/562.misc
new file mode 100644
index 00000000..88d21020
--- /dev/null
+++ b/src/towncrier/newsfragments/562.misc
@@ -0,0 +1 @@
+Improved structure and readability of some tests for building the changelog.
diff --git a/src/towncrier/test/helpers.py b/src/towncrier/test/helpers.py
index ddc9ffc6..366e1ae5 100644
--- a/src/towncrier/test/helpers.py
+++ b/src/towncrier/test/helpers.py
@@ -5,6 +5,7 @@
 
 from functools import wraps
 from pathlib import Path
+from subprocess import call
 from typing import Any, Callable
 
 from click.testing import CliRunner
@@ -62,10 +63,78 @@ def setup_simple_project(
 ) -> None:
     if config is None:
         config = "[tool.towncrier]\n" 'package = "foo"\n' + extra_config
-
+    else:
+        config = textwrap.dedent(config)
     Path(pyproject_path).write_text(config)
     Path("foo").mkdir()
     Path("foo/__init__.py").write_text('__version__ = "1.2.3"\n')
 
     if mkdir_newsfragments:
         Path("foo/newsfragments").mkdir()
+
+
+def with_project(
+    *,
+    config: str | None = None,
+    pyproject_path: str = "pyproject.toml",
+) -> Callable[[Callable[..., Any]], Callable[..., Any]]:
+    """Decorator to run a test with an isolated directory containing a simple
+    project.
+    Use `config` to tweak the content of the config file.
+    Use `pyproject_path` to tweak the location of the config file.
+    """
+
+    def decorator(fn: Callable[..., Any]) -> Callable[..., Any]:
+        @wraps(fn)
+        def test(*args: Any, **kw: Any) -> Any:
+            runner = CliRunner()
+            with runner.isolated_filesystem():
+                setup_simple_project(
+                    config=config,
+                    pyproject_path=pyproject_path,
+                )
+
+                return fn(*args, runner=runner, **kw)
+
+        return test
+
+    return decorator
+
+
+def with_git_project(
+    *,
+    config: str | None = None,
+    pyproject_path: str = "pyproject.toml",
+) -> Callable[[Callable[..., Any]], Callable[..., Any]]:
+    """Decorator to run a test with an isolated directory containing a simple
+    project checked into git.
+    Use `config` to tweak the content of the config file.
+    Use `pyproject_path` to tweak the location of the config file.
+    """
+
+    def decorator(fn: Callable[..., Any]) -> Callable[..., Any]:
+        def _commit() -> None:
+            call(["git", "add", "."])
+            call(["git", "commit", "-m", "Second Commit"])
+
+        @wraps(fn)
+        def test(*args: Any, **kw: Any) -> Any:
+            runner = CliRunner()
+            with runner.isolated_filesystem():
+                setup_simple_project(
+                    config=config,
+                    pyproject_path=pyproject_path,
+                )
+
+                call(["git", "init"])
+                call(["git", "config", "user.name", "user"])
+                call(["git", "config", "user.email", "user@example.com"])
+                call(["git", "config", "commit.gpgSign", "false"])
+                call(["git", "add", "."])
+                call(["git", "commit", "-m", "Initial Commit"])
+
+                return fn(*args, runner=runner, commit=_commit, **kw)
+
+        return test
+
+    return decorator
diff --git a/src/towncrier/test/test_build.py b/src/towncrier/test/test_build.py
index 938814cc..76f6e8aa 100644
--- a/src/towncrier/test/test_build.py
+++ b/src/towncrier/test/test_build.py
@@ -6,7 +6,6 @@
 
 from datetime import date
 from pathlib import Path
-from subprocess import call
 from textwrap import dedent
 from unittest.mock import patch
 
@@ -15,50 +14,48 @@
 
 from .._shell import cli
 from ..build import _main
-from .helpers import read, setup_simple_project, with_isolated_runner, write
+from .helpers import read, with_git_project, with_project, write
 
 
 class TestCli(TestCase):
     maxDiff = None
 
-    def _test_command(self, command):
-        runner = CliRunner()
-
-        with runner.isolated_filesystem():
-            setup_simple_project()
-            with open("foo/newsfragments/123.feature", "w") as f:
-                f.write("Adds levitation")
-            # Towncrier treats this as 124.feature, ignoring .rst extension
-            with open("foo/newsfragments/124.feature.rst", "w") as f:
-                f.write("Extends levitation")
-            # Towncrier supports non-numeric newsfragment names.
-            with open("foo/newsfragments/baz.feature.rst", "w") as f:
-                f.write("Baz levitation")
-            # Towncrier supports files that have a dot in the name of the
-            # newsfragment
-            with open("foo/newsfragments/fix-1.2.feature", "w") as f:
-                f.write("Baz fix levitation")
-            # Towncrier supports fragments not linked to a feature
-            with open("foo/newsfragments/+anything.feature", "w") as f:
-                f.write("Orphaned feature")
-            with open("foo/newsfragments/+xxx.feature", "w") as f:
-                f.write("Another orphaned feature")
-            with open("foo/newsfragments/+123_orphaned.feature", "w") as f:
-                f.write("An orphaned feature starting with a number")
-            with open("foo/newsfragments/+12.3_orphaned.feature", "w") as f:
-                f.write("An orphaned feature starting with a dotted number")
-            with open("foo/newsfragments/+orphaned_123.feature", "w") as f:
-                f.write("An orphaned feature ending with a number")
-            with open("foo/newsfragments/+orphaned_12.3.feature", "w") as f:
-                f.write("An orphaned feature ending with a dotted number")
-            # Towncrier ignores files that don't have a dot
-            with open("foo/newsfragments/README", "w") as f:
-                f.write("Blah blah")
-            # And files that don't have a valid category
-            with open("foo/newsfragments/README.rst", "w") as f:
-                f.write("**Blah blah**")
-
-            result = runner.invoke(command, ["--draft", "--date", "01-01-2001"])
+    @with_project()
+    def _test_command(self, command, runner):
+        # Off the shelf newsfragment
+        with open("foo/newsfragments/123.feature", "w") as f:
+            f.write("Adds levitation")
+        # Towncrier treats this as 124.feature, ignoring .rst extension
+        with open("foo/newsfragments/124.feature.rst", "w") as f:
+            f.write("Extends levitation")
+        # Towncrier supports non-numeric newsfragment names.
+        with open("foo/newsfragments/baz.feature.rst", "w") as f:
+            f.write("Baz levitation")
+        # Towncrier supports files that have a dot in the name of the
+        # newsfragment
+        with open("foo/newsfragments/fix-1.2.feature", "w") as f:
+            f.write("Baz fix levitation")
+        # Towncrier supports fragments not linked to a feature
+        with open("foo/newsfragments/+anything.feature", "w") as f:
+            f.write("Orphaned feature")
+        with open("foo/newsfragments/+xxx.feature", "w") as f:
+            f.write("Another orphaned feature")
+        with open("foo/newsfragments/+123_orphaned.feature", "w") as f:
+            f.write("An orphaned feature starting with a number")
+        with open("foo/newsfragments/+12.3_orphaned.feature", "w") as f:
+            f.write("An orphaned feature starting with a dotted number")
+        with open("foo/newsfragments/+orphaned_123.feature", "w") as f:
+            f.write("An orphaned feature ending with a number")
+        with open("foo/newsfragments/+orphaned_12.3.feature", "w") as f:
+            f.write("An orphaned feature ending with a dotted number")
+        # Towncrier ignores files that don't have a dot
+        with open("foo/newsfragments/README", "w") as f:
+            f.write("Blah blah")
+        # And files that don't have a valid category
+        with open("foo/newsfragments/README.rst", "w") as f:
+            f.write("**Blah blah**")
+
+        result = runner.invoke(command, ["--draft", "--date", "01-01-2001"])
 
         self.assertEqual(0, result.exit_code, result.output)
         self.assertEqual(
@@ -100,7 +97,7 @@ def test_command(self):
     def test_subcommand(self):
         self._test_command(_main)
 
-    @with_isolated_runner
+    @with_project()
     def test_in_different_dir_dir_option(self, runner):
         """
         The current working directory doesn't matter as long as we pass
@@ -108,7 +105,6 @@ def test_in_different_dir_dir_option(self, runner):
         """
         project_dir = Path(".").resolve()
 
-        setup_simple_project()
         Path("foo/newsfragments/123.feature").write_text("Adds levitation")
         # Ensure our assetion below is meaningful.
         self.assertFalse((project_dir / "NEWS.rst").exists())
@@ -125,7 +121,7 @@ def test_in_different_dir_dir_option(self, runner):
         self.assertEqual(0, result.exit_code)
         self.assertTrue((project_dir / "NEWS.rst").exists())
 
-    @with_isolated_runner
+    @with_project()
     def test_in_different_dir_config_option(self, runner):
         """
         The current working directory and the location of the configuration
@@ -134,7 +130,6 @@ def test_in_different_dir_config_option(self, runner):
         """
         project_dir = Path(".").resolve()
 
-        setup_simple_project()
         Path("foo/newsfragments/123.feature").write_text("Adds levitation")
         # Ensure our assetion below is meaningful.
         self.assertFalse((project_dir / "NEWS.rst").exists())
@@ -157,7 +152,12 @@ def test_in_different_dir_config_option(self, runner):
         self.assertEqual(0, result.exit_code)
         self.assertTrue((project_dir / "NEWS.rst").exists())
 
-    @with_isolated_runner
+    @with_project(
+        config="""
+        [tool.towncrier]
+        directory = "changelog.d"
+        """
+    )
     def test_in_different_dir_with_nondefault_newsfragments_directory(self, runner):
         """
         Using the `--dir` CLI argument, the NEWS file can
@@ -167,9 +167,6 @@ def test_in_different_dir_with_nondefault_newsfragments_directory(self, runner):
         The path passed to `--dir` becomes the
         working directory.
         """
-        Path("pyproject.toml").write_text(
-            "[tool.towncrier]\n" + 'directory = "changelog.d"\n'
-        )
         Path("foo/foo").mkdir(parents=True)
         Path("foo/foo/__init__.py").write_text("")
         Path("foo/changelog.d").mkdir()
@@ -184,12 +181,11 @@ def test_in_different_dir_with_nondefault_newsfragments_directory(self, runner):
         self.assertEqual(0, result.exit_code)
         self.assertTrue(Path("foo/NEWS.rst").exists())
 
-    @with_isolated_runner
+    @with_project()
     def test_no_newsfragment_directory(self, runner):
         """
         A missing newsfragment directory acts as if there are no changes.
         """
-        setup_simple_project()
         os.rmdir("foo/newsfragments")
 
         result = runner.invoke(_main, ["--draft", "--date", "01-01-2001"])
@@ -197,49 +193,38 @@ def test_no_newsfragment_directory(self, runner):
         self.assertEqual(0, result.exit_code)
         self.assertIn("No significant changes.\n", result.output)
 
-    def test_no_newsfragments_draft(self):
+    @with_project()
+    def test_no_newsfragments_draft(self, runner):
         """
         An empty newsfragment directory acts as if there are no changes.
         """
-        runner = CliRunner()
-
-        with runner.isolated_filesystem():
-            setup_simple_project()
-
-            result = runner.invoke(_main, ["--draft", "--date", "01-01-2001"])
+        result = runner.invoke(_main, ["--draft", "--date", "01-01-2001"])
 
         self.assertEqual(0, result.exit_code)
         self.assertIn("No significant changes.\n", result.output)
 
-    def test_no_newsfragments(self):
+    @with_project()
+    def test_no_newsfragments(self, runner):
         """
         An empty newsfragment directory acts as if there are no changes and
         removing files handles it gracefully.
         """
-        runner = CliRunner()
-
-        with runner.isolated_filesystem():
-            setup_simple_project()
+        result = runner.invoke(_main, ["--date", "01-01-2001"])
 
-            result = runner.invoke(_main, ["--date", "01-01-2001"])
-
-            news = read("NEWS.rst")
+        news = read("NEWS.rst")
 
         self.assertEqual(0, result.exit_code)
         self.assertIn("No significant changes.\n", news)
 
-    def test_collision(self):
-        runner = CliRunner()
-
-        with runner.isolated_filesystem():
-            setup_simple_project()
-            # Note that both are 123.feature
-            with open("foo/newsfragments/123.feature", "w") as f:
-                f.write("Adds levitation")
-            with open("foo/newsfragments/123.feature.rst", "w") as f:
-                f.write("Extends levitation")
+    @with_project()
+    def test_collision(self, runner):
+        # Note that both are 123.feature
+        with open("foo/newsfragments/123.feature", "w") as f:
+            f.write("Adds levitation")
+        with open("foo/newsfragments/123.feature.rst", "w") as f:
+            f.write("Extends levitation")
 
-            result = runner.invoke(_main, ["--draft", "--date", "01-01-2001"])
+        result = runner.invoke(_main, ["--draft", "--date", "01-01-2001"])
 
         # This should fail
         self.assertEqual(type(result.exception), ValueError)
@@ -399,69 +384,52 @@ def run_order_scenario(sections, types):
             ),
         )
 
-    def test_draft_no_date(self):
+    @with_git_project()
+    def test_draft_no_date(self, runner, commit):
         """
         If no date is passed, today's date is used.
         """
-        runner = CliRunner()
+        fragment_path1 = "foo/newsfragments/123.feature"
+        fragment_path2 = "foo/newsfragments/124.feature.rst"
+        with open(fragment_path1, "w") as f:
+            f.write("Adds levitation")
+        with open(fragment_path2, "w") as f:
+            f.write("Extends levitation")
 
-        with runner.isolated_filesystem():
-            setup_simple_project()
-            fragment_path1 = "foo/newsfragments/123.feature"
-            fragment_path2 = "foo/newsfragments/124.feature.rst"
-            with open(fragment_path1, "w") as f:
-                f.write("Adds levitation")
-            with open(fragment_path2, "w") as f:
-                f.write("Extends levitation")
-
-            call(["git", "init"])
-            call(["git", "config", "user.name", "user"])
-            call(["git", "config", "user.email", "user@example.com"])
-            call(["git", "config", "commit.gpgSign", "false"])
-            call(["git", "add", "."])
-            call(["git", "commit", "-m", "Initial Commit"])
-
-            today = date.today()
-            result = runner.invoke(_main, ["--draft"])
+        commit()
 
-            self.assertEqual(0, result.exit_code)
-            self.assertIn(f"Foo 1.2.3 ({today.isoformat()})", result.output)
+        today = date.today()
+        result = runner.invoke(_main, ["--draft"])
 
-    def test_no_confirmation(self):
-        runner = CliRunner()
+        self.assertEqual(0, result.exit_code)
+        self.assertIn(f"Foo 1.2.3 ({today.isoformat()})", result.output)
 
-        with runner.isolated_filesystem():
-            setup_simple_project()
-            fragment_path1 = "foo/newsfragments/123.feature"
-            fragment_path2 = "foo/newsfragments/124.feature.rst"
-            with open(fragment_path1, "w") as f:
-                f.write("Adds levitation")
-            with open(fragment_path2, "w") as f:
-                f.write("Extends levitation")
-
-            call(["git", "init"])
-            call(["git", "config", "user.name", "user"])
-            call(["git", "config", "user.email", "user@example.com"])
-            call(["git", "config", "commit.gpgSign", "false"])
-            call(["git", "add", "."])
-            call(["git", "commit", "-m", "Initial Commit"])
-
-            result = runner.invoke(_main, ["--date", "01-01-2001", "--yes"])
-
-            self.assertEqual(0, result.exit_code)
-            path = "NEWS.rst"
-            self.assertTrue(os.path.isfile(path))
-            self.assertFalse(os.path.isfile(fragment_path1))
-            self.assertFalse(os.path.isfile(fragment_path2))
-
-    @with_isolated_runner
-    def test_keep_fragments(self, runner):
+    @with_git_project()
+    def test_no_confirmation(self, runner, commit):
+        fragment_path1 = "foo/newsfragments/123.feature"
+        fragment_path2 = "foo/newsfragments/124.feature.rst"
+        with open(fragment_path1, "w") as f:
+            f.write("Adds levitation")
+        with open(fragment_path2, "w") as f:
+            f.write("Extends levitation")
+
+        commit()
+
+        result = runner.invoke(_main, ["--date", "01-01-2001", "--yes"])
+
+        self.assertEqual(0, result.exit_code)
+        path = "NEWS.rst"
+        self.assertTrue(os.path.isfile(path))
+        self.assertFalse(os.path.isfile(fragment_path1))
+        self.assertFalse(os.path.isfile(fragment_path2))
+
+    @with_git_project()
+    def test_keep_fragments(self, runner, commit):
         """
         The `--keep` option will build the full final news file
         without deleting the fragment files and without
         any extra CLI interaction or confirmation.
         """
-        setup_simple_project()
         fragment_path1 = "foo/newsfragments/123.feature"
         fragment_path2 = "foo/newsfragments/124.feature.rst"
         with open(fragment_path1, "w") as f:
@@ -469,12 +437,7 @@ def test_keep_fragments(self, runner):
         with open(fragment_path2, "w") as f:
             f.write("Extends levitation")
 
-        call(["git", "init"])
-        call(["git", "config", "user.name", "user"])
-        call(["git", "config", "user.email", "user@example.com"])
-        call(["git", "config", "commit.gpgSign", "false"])
-        call(["git", "add", "."])
-        call(["git", "commit", "-m", "Initial Commit"])
+        commit()
 
         result = runner.invoke(_main, ["--date", "01-01-2001", "--keep"])
 
@@ -485,8 +448,8 @@ def test_keep_fragments(self, runner):
         self.assertTrue(os.path.isfile(fragment_path1))
         self.assertTrue(os.path.isfile(fragment_path2))
 
-    @with_isolated_runner
-    def test_yes_keep_error(self, runner):
+    @with_git_project()
+    def test_yes_keep_error(self, runner, commit):
         """
         It will fail to perform any action when the
         conflicting --keep and --yes options are provided.
@@ -495,7 +458,6 @@ def test_yes_keep_error(self, runner):
         to make sure both orders are validated since click triggers the validator
         in the order it parses the command line.
         """
-        setup_simple_project()
         fragment_path1 = "foo/newsfragments/123.feature"
         fragment_path2 = "foo/newsfragments/124.feature.rst"
         with open(fragment_path1, "w") as f:
@@ -503,12 +465,7 @@ def test_yes_keep_error(self, runner):
         with open(fragment_path2, "w") as f:
             f.write("Extends levitation")
 
-        call(["git", "init"])
-        call(["git", "config", "user.name", "user"])
-        call(["git", "config", "user.email", "user@example.com"])
-        call(["git", "config", "commit.gpgSign", "false"])
-        call(["git", "add", "."])
-        call(["git", "commit", "-m", "Initial Commit"])
+        commit()
 
         result = runner.invoke(_main, ["--date", "01-01-2001", "--yes", "--keep"])
         self.assertEqual(1, result.exit_code)
@@ -516,38 +473,30 @@ def test_yes_keep_error(self, runner):
         result = runner.invoke(_main, ["--date", "01-01-2001", "--keep", "--yes"])
         self.assertEqual(1, result.exit_code)
 
-    def test_confirmation_says_no(self):
+    @with_git_project()
+    def test_confirmation_says_no(self, runner, commit):
         """
         If the user says "no" to removing the newsfragements, we end up with
         a NEWS.rst AND the newsfragments.
         """
-        runner = CliRunner()
+        fragment_path1 = "foo/newsfragments/123.feature"
+        fragment_path2 = "foo/newsfragments/124.feature.rst"
+        with open(fragment_path1, "w") as f:
+            f.write("Adds levitation")
+        with open(fragment_path2, "w") as f:
+            f.write("Extends levitation")
 
-        with runner.isolated_filesystem():
-            setup_simple_project()
-            fragment_path1 = "foo/newsfragments/123.feature"
-            fragment_path2 = "foo/newsfragments/124.feature.rst"
-            with open(fragment_path1, "w") as f:
-                f.write("Adds levitation")
-            with open(fragment_path2, "w") as f:
-                f.write("Extends levitation")
-
-            call(["git", "init"])
-            call(["git", "config", "user.name", "user"])
-            call(["git", "config", "user.email", "user@example.com"])
-            call(["git", "config", "commit.gpgSign", "false"])
-            call(["git", "add", "."])
-            call(["git", "commit", "-m", "Initial Commit"])
-
-            with patch("towncrier.build.click.confirm") as m:
-                m.return_value = False
-                result = runner.invoke(_main, [])
-
-            self.assertEqual(0, result.exit_code)
-            path = "NEWS.rst"
-            self.assertTrue(os.path.isfile(path))
-            self.assertTrue(os.path.isfile(fragment_path1))
-            self.assertTrue(os.path.isfile(fragment_path2))
+        commit()
+
+        with patch("towncrier.build.click.confirm") as m:
+            m.return_value = False
+            result = runner.invoke(_main, [])
+
+        self.assertEqual(0, result.exit_code)
+        path = "NEWS.rst"
+        self.assertTrue(os.path.isfile(path))
+        self.assertTrue(os.path.isfile(fragment_path1))
+        self.assertTrue(os.path.isfile(fragment_path2))
 
     def test_needs_config(self):
         """
@@ -561,50 +510,45 @@ def test_needs_config(self):
         self.assertEqual(1, result.exit_code, result.output)
         self.assertTrue(result.output.startswith("No configuration file found."))
 
-    @with_isolated_runner
+    @with_project(config="[tool.towncrier]")
     def test_needs_version(self, runner: CliRunner):
         """
         If the configuration file doesn't specify a version or a package, the version
         option is required.
         """
-        write("towncrier.toml", "[tool.towncrier]")
-
         result = runner.invoke(_main, ["--draft"], catch_exceptions=False)
 
         self.assertEqual(2, result.exit_code)
         self.assertIn("Error: '--version' is required", result.output)
 
-    def test_projectless_changelog(self):
+    @with_project()
+    def test_projectless_changelog(self, runner):
         """In which a directory containing news files is built into a changelog
 
         - without a Python project or version number. We override the
         project title from the commandline.
         """
-        runner = CliRunner()
+        # Remove the version from the project
+        Path("foo/__init__.py").unlink()
 
-        with runner.isolated_filesystem():
-            with open("pyproject.toml", "w") as f:
-                f.write("[tool.towncrier]\n" 'package = "foo"\n')
-            os.mkdir("foo")
-            os.mkdir("foo/newsfragments")
-            with open("foo/newsfragments/123.feature", "w") as f:
-                f.write("Adds levitation")
-            # Towncrier ignores .rst extension
-            with open("foo/newsfragments/124.feature.rst", "w") as f:
-                f.write("Extends levitation")
+        with open("foo/newsfragments/123.feature", "w") as f:
+            f.write("Adds levitation")
+        # Towncrier ignores .rst extension
+        with open("foo/newsfragments/124.feature.rst", "w") as f:
+            f.write("Extends levitation")
 
-            result = runner.invoke(
-                _main,
-                [
-                    "--name",
-                    "FooBarBaz",
-                    "--version",
-                    "7.8.9",
-                    "--date",
-                    "01-01-2001",
-                    "--draft",
-                ],
-            )
+        result = runner.invoke(
+            _main,
+            [
+                "--name",
+                "FooBarBaz",
+                "--version",
+                "7.8.9",
+                "--date",
+                "01-01-2001",
+                "--draft",
+            ],
+        )
 
         self.assertEqual(0, result.exit_code)
         self.assertEqual(
@@ -632,22 +576,23 @@ def test_projectless_changelog(self):
             ).lstrip(),
         )
 
-    def test_version_in_config(self):
-        """The calling towncrier with version defined in configfile.
+    @with_project(
+        config="""
+        [tool.towncrier]
+        version = "7.8.9"
+        """
+    )
+    def test_version_in_config(self, runner):
+        """Calling towncrier with version defined in configfile.
 
         Specifying a version in toml file will be helpful if version
         is maintained by i.e. bumpversion and it's not a python project.
         """
-        runner = CliRunner()
-
-        with runner.isolated_filesystem():
-            with open("pyproject.toml", "w") as f:
-                f.write("[tool.towncrier]\n" 'version = "7.8.9"\n')
-            os.mkdir("newsfragments")
-            with open("newsfragments/123.feature", "w") as f:
-                f.write("Adds levitation")
+        os.mkdir("newsfragments")
+        with open("newsfragments/123.feature", "w") as f:
+            f.write("Adds levitation")
 
-            result = runner.invoke(_main, ["--date", "01-01-2001", "--draft"])
+        result = runner.invoke(_main, ["--date", "01-01-2001", "--draft"])
 
         self.assertEqual(0, result.exit_code, result.output)
         self.assertEqual(
@@ -674,24 +619,25 @@ def test_version_in_config(self):
             ).lstrip(),
         )
 
-    def test_project_name_in_config(self):
+    @with_project(
+        config="""
+        [tool.towncrier]
+        name = "ImGoProject"
+        """
+    )
+    def test_project_name_in_config(self, runner):
         """The calling towncrier with project name defined in configfile.
 
         Specifying a project name in toml file will be helpful to keep the
         project name consistent as part of the towncrier configuration, not call.
         """
-        runner = CliRunner()
-
-        with runner.isolated_filesystem():
-            with open("pyproject.toml", "w") as f:
-                f.write("[tool.towncrier]\n" 'name = "ImGoProject"\n')
-            os.mkdir("newsfragments")
-            with open("newsfragments/123.feature", "w") as f:
-                f.write("Adds levitation")
+        os.mkdir("newsfragments")
+        with open("newsfragments/123.feature", "w") as f:
+            f.write("Adds levitation")
 
-            result = runner.invoke(
-                _main, ["--version", "7.8.9", "--date", "01-01-2001", "--draft"]
-            )
+        result = runner.invoke(
+            _main, ["--version", "7.8.9", "--date", "01-01-2001", "--draft"]
+        )
 
         self.assertEqual(0, result.exit_code, result.output)
         self.assertEqual(
@@ -718,7 +664,8 @@ def test_project_name_in_config(self):
             ).lstrip(),
         )
 
-    def test_no_package_changelog(self):
+    @with_project(config="[tool.towncrier]")
+    def test_no_package_changelog(self, runner):
         """The calling towncrier with any package argument.
 
         Specifying a package in the toml file or the command line
@@ -727,18 +674,13 @@ def test_no_package_changelog(self):
           so we do not need the package for that.
         - we don't need to include the package in the changelog header.
         """
-        runner = CliRunner()
-
-        with runner.isolated_filesystem():
-            with open("pyproject.toml", "w") as f:
-                f.write("[tool.towncrier]")
-            os.mkdir("newsfragments")
-            with open("newsfragments/123.feature", "w") as f:
-                f.write("Adds levitation")
+        os.mkdir("newsfragments")
+        with open("newsfragments/123.feature", "w") as f:
+            f.write("Adds levitation")
 
-            result = runner.invoke(
-                _main, ["--version", "7.8.9", "--date", "01-01-2001", "--draft"]
-            )
+        result = runner.invoke(
+            _main, ["--version", "7.8.9", "--date", "01-01-2001", "--draft"]
+        )
 
         self.assertEqual(0, result.exit_code, result.output)
         self.assertEqual(
@@ -765,13 +707,19 @@ def test_no_package_changelog(self):
             ).lstrip(),
         )
 
-    def test_release_notes_in_separate_files(self):
+    @with_project(
+        config="""
+        [tool.towncrier]
+         single_file=false
+         filename="{version}-notes.rst"
+        """
+    )
+    def test_release_notes_in_separate_files(self, runner):
         """
         When `single_file = false` the release notes for each version are stored
         in a separate file.
         The name of the file is defined by the `filename` configuration value.
         """
-        runner = CliRunner()
 
         def do_build_once_with(version, fragment_file, fragment):
             with open(f"newsfragments/{fragment_file}", "w") as f:
@@ -794,78 +742,65 @@ def do_build_once_with(version, fragment_file, fragment):
             return result
 
         results = []
-        with runner.isolated_filesystem():
-            with open("pyproject.toml", "w") as f:
-                f.write(
-                    "\n".join(
-                        [
-                            "[tool.towncrier]",
-                            " single_file=false",
-                            ' filename="{version}-notes.rst"',
-                        ]
-                    )
-                )
-            os.mkdir("newsfragments")
-            results.append(
-                do_build_once_with("7.8.9", "123.feature", "Adds levitation")
-            )
-            results.append(do_build_once_with("7.9.0", "456.bugfix", "Adds catapult"))
+        os.mkdir("newsfragments")
+        results.append(do_build_once_with("7.8.9", "123.feature", "Adds levitation"))
+        results.append(do_build_once_with("7.9.0", "456.bugfix", "Adds catapult"))
 
-            self.assertEqual(0, results[0].exit_code, results[0].output)
-            self.assertEqual(0, results[1].exit_code, results[1].output)
-            self.assertEqual(
-                2,
-                len(list(Path.cwd().glob("*-notes.rst"))),
-                "one newfile for each build",
-            )
-            self.assertTrue(os.path.exists("7.8.9-notes.rst"), os.listdir("."))
-            self.assertTrue(os.path.exists("7.9.0-notes.rst"), os.listdir("."))
+        self.assertEqual(0, results[0].exit_code, results[0].output)
+        self.assertEqual(0, results[1].exit_code, results[1].output)
+        self.assertEqual(
+            2,
+            len(list(Path.cwd().glob("*-notes.rst"))),
+            "one newfile for each build",
+        )
+        self.assertTrue(os.path.exists("7.8.9-notes.rst"), os.listdir("."))
+        self.assertTrue(os.path.exists("7.9.0-notes.rst"), os.listdir("."))
 
-            outputs = []
-            outputs.append(read("7.8.9-notes.rst"))
-            outputs.append(read("7.9.0-notes.rst"))
+        outputs = []
+        outputs.append(read("7.8.9-notes.rst"))
+        outputs.append(read("7.9.0-notes.rst"))
 
-            self.assertEqual(
-                outputs[0],
-                dedent(
-                    """
-                foo 7.8.9 (01-01-2001)
-                ======================
+        self.assertEqual(
+            outputs[0],
+            dedent(
+                """
+            foo 7.8.9 (01-01-2001)
+            ======================
 
-                Features
-                --------
+            Features
+            --------
 
-                - Adds levitation (#123)
+            - Adds levitation (#123)
+            """
+            ).lstrip(),
+        )
+        self.assertEqual(
+            outputs[1],
+            dedent(
                 """
-                ).lstrip(),
-            )
-            self.assertEqual(
-                outputs[1],
-                dedent(
-                    """
-                foo 7.9.0 (01-01-2001)
-                ======================
+            foo 7.9.0 (01-01-2001)
+            ======================
 
-                Bugfixes
-                --------
+            Bugfixes
+            --------
 
-                - Adds catapult (#456)
-                """
-                ).lstrip(),
-            )
+            - Adds catapult (#456)
+            """
+            ).lstrip(),
+        )
 
-    def test_singlefile_errors_and_explains_cleanly(self):
+    @with_project(
+        config="""
+        [tool.towncrier]
+        singlefile="fail!"
+        """
+    )
+    def test_singlefile_errors_and_explains_cleanly(self, runner):
         """
         Failure to find the configuration file results in a clean explanation
         without a traceback.
         """
-        runner = CliRunner()
-
-        with runner.isolated_filesystem():
-            with open("pyproject.toml", "w") as f:
-                f.write('[tool.towncrier]\n singlefile="fail!"\n')
-
-            result = runner.invoke(_main)
+        result = runner.invoke(_main)
 
         self.assertEqual(1, result.exit_code)
         self.assertEqual(
@@ -958,123 +893,115 @@ def do_build_once_with(version, fragment_file, fragment):
                 ).lstrip(),
             )
 
-    def test_bullet_points_false(self):
+    @with_project(
+        config="""
+        [tool.towncrier]
+        template="towncrier:single-file-no-bullets"
+        all_bullets=false
+        """
+    )
+    def test_bullet_points_false(self, runner):
         """
         When all_bullets is false, subsequent lines are not indented.
 
         The automatic ticket number inserted by towncrier will align with the
         manual bullet.
         """
-        runner = CliRunner()
+        os.mkdir("newsfragments")
+        with open("newsfragments/123.feature", "w") as f:
+            f.write("wow!\n~~~~\n\nNo indentation at all.")
+        with open("newsfragments/124.bugfix", "w") as f:
+            f.write("#. Numbered bullet list.")
+        with open("newsfragments/125.removal", "w") as f:
+            f.write("- Hyphen based bullet list.")
+        with open("newsfragments/126.doc", "w") as f:
+            f.write("* Asterisk based bullet list.")
 
-        with runner.isolated_filesystem():
-            with open("pyproject.toml", "w") as f:
-                f.write(
-                    "[tool.towncrier]\n"
-                    'template="towncrier:single-file-no-bullets"\n'
-                    "all_bullets=false"
-                )
-            os.mkdir("newsfragments")
-            with open("newsfragments/123.feature", "w") as f:
-                f.write("wow!\n~~~~\n\nNo indentation at all.")
-            with open("newsfragments/124.bugfix", "w") as f:
-                f.write("#. Numbered bullet list.")
-            with open("newsfragments/125.removal", "w") as f:
-                f.write("- Hyphen based bullet list.")
-            with open("newsfragments/126.doc", "w") as f:
-                f.write("* Asterisk based bullet list.")
-
-            result = runner.invoke(
-                _main,
-                [
-                    "--version",
-                    "7.8.9",
-                    "--name",
-                    "foo",
-                    "--date",
-                    "01-01-2001",
-                    "--yes",
-                ],
-            )
+        result = runner.invoke(
+            _main,
+            [
+                "--version",
+                "7.8.9",
+                "--name",
+                "foo",
+                "--date",
+                "01-01-2001",
+                "--yes",
+            ],
+        )
 
-            self.assertEqual(0, result.exit_code, result.output)
-            output = read("NEWS.rst")
+        self.assertEqual(0, result.exit_code, result.output)
+        output = read("NEWS.rst")
 
         self.assertEqual(
             output,
-            """
-foo 7.8.9 (01-01-2001)
-======================
+            dedent(
+                """
+                foo 7.8.9 (01-01-2001)
+                ======================
 
-Features
---------
+                Features
+                --------
 
-wow!
-~~~~
+                wow!
+                ~~~~
 
-No indentation at all.
-(#123)
+                No indentation at all.
+                (#123)
 
 
-Bugfixes
---------
+                Bugfixes
+                --------
 
-#. Numbered bullet list.
-   (#124)
+                #. Numbered bullet list.
+                   (#124)
 
 
-Improved Documentation
-----------------------
+                Improved Documentation
+                ----------------------
 
-* Asterisk based bullet list.
-  (#126)
+                * Asterisk based bullet list.
+                  (#126)
 
 
-Deprecations and Removals
--------------------------
+                Deprecations and Removals
+                -------------------------
 
-- Hyphen based bullet list.
-  (#125)
-""".lstrip(),
+                - Hyphen based bullet list.
+                  (#125)
+                """
+            ).lstrip(),
         )
 
-    def test_title_format_custom(self):
+    @with_project(
+        config="""
+        [tool.towncrier]
+        package = "foo"
+        title_format = "[{project_date}] CUSTOM RELEASE for {name} version {version}"
+        """
+    )
+    def test_title_format_custom(self, runner):
         """
         A non-empty title format adds the specified title.
         """
-        runner = CliRunner()
-
-        with runner.isolated_filesystem():
-            with open("pyproject.toml", "w") as f:
-                f.write(
-                    dedent(
-                        """\
-                    [tool.towncrier]
-                    package = "foo"
-                    title_format = "[{project_date}] CUSTOM RELEASE for {name} version {version}"
-                """
-                    )
-                )
-            os.mkdir("foo")
-            os.mkdir("foo/newsfragments")
-            with open("foo/newsfragments/123.feature", "w") as f:
-                f.write("Adds levitation")
-            # Towncrier ignores .rst extension
-            with open("foo/newsfragments/124.feature.rst", "w") as f:
-                f.write("Extends levitation")
+        with open("foo/newsfragments/123.feature", "w") as f:
+            f.write("Adds levitation")
+        # Towncrier ignores .rst extension
+        with open("foo/newsfragments/124.feature.rst", "w") as f:
+            f.write("Extends levitation")
 
-            result = runner.invoke(
-                _main,
-                [
-                    "--name",
-                    "FooBarBaz",
-                    "--version",
-                    "7.8.9",
-                    "--date",
-                    "20-01-2001",
-                    "--draft",
-                ],
-            )
+        result = runner.invoke(
+            _main,
+            [
+                "--name",
+                "FooBarBaz",
+                "--version",
+                "7.8.9",
+                "--date",
+                "20-01-2001",
+                "--draft",
+            ],
+        )
 
         expected_output = dedent(
             """\
@@ -1101,61 +1028,53 @@ def test_title_format_custom(self):
         self.assertEqual(0, result.exit_code)
         self.assertEqual(expected_output, result.output)
 
-    def test_title_format_false(self):
+    @with_project(
+        config="""
+        [tool.towncrier]
+        package = "foo"
+        title_format = false
+        template = "template.rst"
+        """
+    )
+    def test_title_format_false(self, runner):
         """
         Setting the title format to false disables the explicit title.  This
         would be used, for example, when the template creates the title itself.
         """
-        runner = CliRunner()
-
-        with runner.isolated_filesystem():
-            with open("pyproject.toml", "w") as f:
-                f.write(
-                    dedent(
-                        """\
-                    [tool.towncrier]
-                    package = "foo"
-                    title_format = false
-                    template = "template.rst"
-                """
-                    )
-                )
-            os.mkdir("foo")
-            os.mkdir("foo/newsfragments")
-            with open("template.rst", "w") as f:
-                f.write(
-                    dedent(
-                        """\
-                    Here's a hardcoded title added by the template
-                    ==============================================
-                    {% for section in sections %}
-                    {% set underline = "-" %}
-                    {% for category, val in definitions.items() if category in sections[section] %}
-
-                    {% for text, values in sections[section][category]|dictsort(by='value') %}
-                    - {{ text }}
-
-                    {% endfor %}
-                    {% endfor %}
-                    {% endfor %}
-                """
-                    )
+        with open("template.rst", "w") as f:
+            f.write(
+                dedent(
+                    """\
+                Here's a hardcoded title added by the template
+                ==============================================
+                {% for section in sections %}
+                {% set underline = "-" %}
+                {% for category, val in definitions.items() if category in sections[section] %}
+
+                {% for text, values in sections[section][category]|dictsort(by='value') %}
+                - {{ text }}
+
+                {% endfor %}
+                {% endfor %}
+                {% endfor %}
+            """
                 )
-
-            result = runner.invoke(
-                _main,
-                [
-                    "--name",
-                    "FooBarBaz",
-                    "--version",
-                    "7.8.9",
-                    "--date",
-                    "20-01-2001",
-                    "--draft",
-                ],
-                catch_exceptions=False,
             )
 
+        result = runner.invoke(
+            _main,
+            [
+                "--name",
+                "FooBarBaz",
+                "--version",
+                "7.8.9",
+                "--date",
+                "20-01-2001",
+                "--draft",
+            ],
+            catch_exceptions=False,
+        )
+
         expected_output = dedent(
             """\
             Loading template...
@@ -1173,46 +1092,40 @@ def test_title_format_false(self):
         self.assertEqual(0, result.exit_code)
         self.assertEqual(expected_output, result.output)
 
-    def test_start_string(self):
+    @with_project(
+        config="""
+        [tool.towncrier]
+        start_string="Release notes start marker"
+        """
+    )
+    def test_start_string(self, runner):
         """
         The `start_string` configuration is used to detect the starting point
         for inserting the generated release notes. A newline is automatically
         added to the configured value.
         """
-        runner = CliRunner()
-
-        with runner.isolated_filesystem():
-            with open("pyproject.toml", "w") as f:
-                f.write(
-                    dedent(
-                        """\
-                    [tool.towncrier]
-                    start_string="Release notes start marker"
-                """
-                    )
-                )
-            os.mkdir("newsfragments")
-            with open("newsfragments/123.feature", "w") as f:
-                f.write("Adds levitation")
-            with open("NEWS.rst", "w") as f:
-                f.write("a line\n\nanother\n\nRelease notes start marker\na footer!\n")
+        os.mkdir("newsfragments")
+        with open("newsfragments/123.feature", "w") as f:
+            f.write("Adds levitation")
+        with open("NEWS.rst", "w") as f:
+            f.write("a line\n\nanother\n\nRelease notes start marker\na footer!\n")
 
-            result = runner.invoke(
-                _main,
-                [
-                    "--version",
-                    "7.8.9",
-                    "--name",
-                    "foo",
-                    "--date",
-                    "01-01-2001",
-                    "--yes",
-                ],
-            )
+        result = runner.invoke(
+            _main,
+            [
+                "--version",
+                "7.8.9",
+                "--name",
+                "foo",
+                "--date",
+                "01-01-2001",
+                "--yes",
+            ],
+        )
 
-            self.assertEqual(0, result.exit_code, result.output)
-            self.assertTrue(os.path.exists("NEWS.rst"), os.listdir("."))
-            output = read("NEWS.rst")
+        self.assertEqual(0, result.exit_code, result.output)
+        self.assertTrue(os.path.exists("NEWS.rst"), os.listdir("."))
+        output = read("NEWS.rst")
 
         expected_output = dedent(
             """\
@@ -1236,13 +1149,11 @@ def test_start_string(self):
 
         self.assertEqual(expected_output, output)
 
-    @with_isolated_runner
+    @with_project()
     def test_default_start_string(self, runner):
         """
         The default start string is ``.. towncrier release notes start``.
         """
-        setup_simple_project()
-
         write("foo/newsfragments/123.feature", "Adds levitation")
         write(
             "NEWS.rst",
@@ -1285,14 +1196,18 @@ def test_default_start_string(self, runner):
 
         self.assertEqual(expected_output, output)
 
-    @with_isolated_runner
+    @with_project(
+        config="""
+        [tool.towncrier]
+        package = "foo"
+        filename = "NEWS.md"
+        """
+    )
     def test_default_start_string_markdown(self, runner):
         """
         The default start string is ``<!-- towncrier release notes start -->`` for
         Markdown.
         """
-        setup_simple_project(extra_config='filename = "NEWS.md"')
-
         write("foo/newsfragments/123.feature", "Adds levitation")
         write(
             "NEWS.md",
@@ -1333,59 +1248,53 @@ def test_default_start_string_markdown(self, runner):
 
         self.assertEqual(expected_output, output)
 
-    def test_with_topline_and_template_and_draft(self):
+    @with_project(
+        config="""
+        [tool.towncrier]
+        title_format = "{version} - {project_date}"
+        template = "template.rst"
+
+          [[tool.towncrier.type]]
+          directory = "feature"
+          name = ""
+          showcontent = true
+        """
+    )
+    def test_with_topline_and_template_and_draft(self, runner):
         """
         Spacing is proper when drafting with a topline and a template.
         """
-        runner = CliRunner()
+        os.mkdir("newsfragments")
+        with open("newsfragments/123.feature", "w") as f:
+            f.write("Adds levitation")
+        with open("template.rst", "w") as f:
+            f.write(
+                dedent(
+                    """\
+                {% for section in sections %}
+                {% set underline = "-" %}
+                {% for category, val in definitions.items() if category in sections[section] %}
 
-        with runner.isolated_filesystem():
-            with open("pyproject.toml", "w") as f:
-                f.write(
-                    dedent(
-                        """\
-                    [tool.towncrier]
-                    title_format = "{version} - {project_date}"
-                    template = "template.rst"
+                {% for text, values in sections[section][category]|dictsort(by='value') %}
+                - {{ text }}
 
-                      [[tool.towncrier.type]]
-                      directory = "feature"
-                      name = ""
-                      showcontent = true
-                """
-                    )
-                )
-            os.mkdir("newsfragments")
-            with open("newsfragments/123.feature", "w") as f:
-                f.write("Adds levitation")
-            with open("template.rst", "w") as f:
-                f.write(
-                    dedent(
-                        """\
-                    {% for section in sections %}
-                    {% set underline = "-" %}
-                    {% for category, val in definitions.items() if category in sections[section] %}
-
-                    {% for text, values in sections[section][category]|dictsort(by='value') %}
-                    - {{ text }}
-
-                    {% endfor %}
-                    {% endfor %}
-                    {% endfor %}
-                """
-                    )
+                {% endfor %}
+                {% endfor %}
+                {% endfor %}
+            """
                 )
-
-            result = runner.invoke(
-                _main,
-                [
-                    "--version=7.8.9",
-                    "--name=foo",
-                    "--date=20-01-2001",
-                    "--draft",
-                ],
             )
 
+        result = runner.invoke(
+            _main,
+            [
+                "--version=7.8.9",
+                "--name=foo",
+                "--date=20-01-2001",
+                "--draft",
+            ],
+        )
+
         expected_output = dedent(
             """\
             Loading template...