Add unit tests for configfile/cmdline processing

src/darker/tests/conftest.py

@@ -1,8 +1,11 @@
 import sys
 import types
+from subprocess import check_call
+from typing import Dict
 from unittest.mock import patch
 
 import pytest
+from py.path import local as LocalPath
 
 
 @pytest.fixture
@@ -15,3 +18,28 @@ def without_isort():
 def with_isort():
     with patch.dict(sys.modules, {"isort": types.ModuleType("isort")}):
         yield
+
+
+class GitRepoFixture:
+    def __init__(self, root: LocalPath):
+        self.root = root
+
+    def add(
+        self, paths_and_contents: Dict[str, str], commit: str = None
+    ) -> Dict[str, LocalPath]:
+        absolute_paths = {
+            relative_path: self.root / relative_path
+            for relative_path in paths_and_contents
+        }
+        for relative_path, content in paths_and_contents.items():
+            absolute_paths[relative_path].write(content)
+            check_call(["git", "add", relative_path], cwd=self.root)
+        if commit:
+            check_call(["git", "commit", "-m", commit], cwd=self.root)
+        return absolute_paths
+
+
+@pytest.fixture
+def git_repo(tmpdir):
+    check_call(["git", "init"], cwd=tmpdir)
+    return GitRepoFixture(tmpdir)

src/darker/tests/test_black_diff.py

@@ -151,13 +151,32 @@ def test_mixed():
     ]
 
 
-@pytest.mark.parametrize("config,line_length", ((None, 79), ("custom.toml", 99)))
-def test_black_config(tmpdir, config, line_length):
+@pytest.mark.parametrize(
+    "config_path, config_lines, expect",
+    [
+        (None, ['line-length = 79'], {'line_length': 79}),
+        ("custom.toml", ['line-length = 99'], {'line_length': 99}),
+        (
+            "custom.toml",
+            ['skip-string-normalization = true'],
+            {'skip_string_normalization': True},
+        ),
+        (
+            "custom.toml",
+            ['skip-string-normalization = false'],
+            {'skip_string_normalization': False},
+        ),
+        ("custom.toml", ["target-version = ['py37']"], {}),
+        ("custom.toml", ["include = '\\.pyi$'"], {}),
+        ("custom.toml", ["exclude = '\\.pyx$'"], {}),
+    ],
+)
+def test_black_config(tmpdir, config_path, config_lines, expect):
     tmpdir = Path(tmpdir)
     src = tmpdir / "src.py"
-    toml = tmpdir / (config or "pyproject.toml")
+    toml = tmpdir / (config_path or "pyproject.toml")
 
-    toml.write_text("[tool.black]\nline-length = {}\n".format(line_length))
+    toml.write_text("[tool.black]\n{}\n".format('\n'.join(config_lines)))
 
-    config = read_black_config(src, config and str(toml))
-    assert config == {"line_length": line_length}
+    config = read_black_config(src, config_path and str(toml))
+    assert config == expect

src/darker/tests/test_command_line.py

@@ -1,7 +1,11 @@
 import re
+from textwrap import dedent
+from unittest.mock import call, patch
 
 import pytest
 
+from darker import black_diff
+from darker.__main__ import main
 from darker.command_line import parse_command_line
 
 
@@ -28,3 +32,49 @@ def test_help_isort_option_without_isort_package(without_isort, darker_help_outp
 
 def test_help_with_isort_package(with_isort, darker_help_output):
     assert "Please run" not in darker_help_output
+
+
+@pytest.mark.parametrize(
+    "options, expect",
+    [
+        ([], call()),
+        (['-c', 'black.cfg'], call(line_length=81, string_normalization=True)),
+        (['--config', 'black.cfg'], call(line_length=81, string_normalization=True)),
+        (['-S'], call(string_normalization=False)),
+        (['--skip-string-normalization'], call(string_normalization=False)),
+        (['-l', '90'], call(line_length=90)),
+        (['--line-length', '90'], call(line_length=90)),
+        (['-c', 'black.cfg', '-S'], call(line_length=81, string_normalization=False)),
+        (
+            ['-c', 'black.cfg', '-l', '90'],
+            call(line_length=90, string_normalization=True),
+        ),
+        (['-l', '90', '-S'], call(line_length=90, string_normalization=False)),
+        (
+            ['-c', 'black.cfg', '-l', '90', '-S'],
+            call(line_length=90, string_normalization=False),
+        ),
+    ],
+)
+def test_black_options(monkeypatch, tmpdir, git_repo, options, expect):
+    monkeypatch.chdir(tmpdir)
+    (tmpdir / 'pyproject.toml').write("[tool.black]\n")
+    (tmpdir / 'black.cfg').write(
+        dedent(
+            """
+            [tool.black]
+            line-length = 81
+            skip-string-normalization = false
+            """
+        )
+    )
+    added_files = git_repo.add(
+        {"main.py": 'print("Hello World!")\n'}, commit="Initial commit"
+    )
+    added_files["main.py"].write('print ("Hello World!")\n')
+    with patch.object(black_diff, 'FileMode', wraps=black_diff.FileMode) as FileMode:
+
+        main(options + [str(path) for path in added_files.values()])
+
+    _, expect_args, expect_kwargs = expect
+    FileMode.assert_called_once_with(*expect_args, **expect_kwargs)