Add Runner interface.

tests/runner_test.py

@@ -0,0 +1,55 @@
+
+import os
+import os.path
+import pytest
+
+import pre_commit.constants as C
+from pre_commit.runner import Runner
+
+
+def test_init_has_no_side_effects(tmpdir):
+    current_wd = os.getcwd()
+    runner = Runner(tmpdir.strpath)
+    assert runner.git_root == tmpdir.strpath
+    assert os.getcwd() == current_wd
+
+
+def test_create_sets_correct_directory(empty_git_dir):
+    runner = Runner.create()
+    assert runner.git_root == empty_git_dir
+    assert os.getcwd() == empty_git_dir
+
+
+@pytest.yield_fixture
+def git_dir_with_directory(empty_git_dir):
+    os.mkdir('foo')
+    yield empty_git_dir
+
+
+def test_changes_to_root_of_git_dir(git_dir_with_directory):
+    os.chdir('foo')
+    assert os.getcwd() != git_dir_with_directory
+    runner = Runner.create()
+    assert runner.git_root == git_dir_with_directory
+    assert os.getcwd() == git_dir_with_directory
+
+
+def test_hooks_workspace_path():
+    runner = Runner('foo/bar')
+    expected_path = os.path.join('foo/bar', C.HOOKS_WORKSPACE)
+    assert runner.hooks_workspace_path == expected_path
+
+
+def test_config_file_path():
+    runner = Runner('foo/bar')
+    expected_path = os.path.join('foo/bar', C.CONFIG_FILE)
+    assert runner.config_file_path == expected_path
+
+
+def test_repositories(consumer_repo):
+    runner = Runner(consumer_repo)
+    assert len(runner.repositories) == 2
+    assert [repo.repo_url for repo in runner.repositories] == [
+        'git@github.com:pre-commit/pre-commit-hooks',
+        'git@github.com:pre-commit/pre-commit',
+    ]