old_contents: from __future__ import absolute_import, division, print_function
  from _pytest.main import EXIT_NOTESTSCOLLECTED
  import pytest
  
  def test_version(testdir, pytestconfig):
      result = testdir.runpytest("--version")
      assert result.ret == 0
      #p = py.path.local(py.__file__).dirpath()
      result.stderr.fnmatch_lines([
          '*pytest*%s*imported from*' % (pytest.__version__, )
      ])
      if pytestconfig.pluginmanager.list_plugin_distinfo():
          result.stderr.fnmatch_lines([
              "*setuptools registered plugins:",
              "*at*",
          ])
  
  def test_help(testdir):
      result = testdir.runpytest("--help")
      assert result.ret == 0
      result.stdout.fnmatch_lines("""
          *-v*verbose*
          *setup.cfg*
          *minversion*
          *to see*markers*pytest --markers*
          *to see*fixtures*pytest --fixtures*
      """)
  
  def test_hookvalidation_unknown(testdir):
      testdir.makeconftest("""
          def pytest_hello(xyz):
              pass
      """)
      result = testdir.runpytest()
      assert result.ret != 0
      result.stderr.fnmatch_lines([
          '*unknown hook*pytest_hello*'
      ])
  
  def test_hookvalidation_optional(testdir):
      testdir.makeconftest("""
          import pytest
          @pytest.hookimpl(optionalhook=True)
          def pytest_hello(xyz):
              pass
      """)
      result = testdir.runpytest()
      assert result.ret == EXIT_NOTESTSCOLLECTED
  
  def test_traceconfig(testdir):
      result = testdir.runpytest("--traceconfig")
      result.stdout.fnmatch_lines([
          "*using*pytest*py*",
          "*active plugins*",
      ])
  
  def test_debug(testdir, monkeypatch):
      result = testdir.runpytest_subprocess("--debug")
      assert result.ret == EXIT_NOTESTSCOLLECTED
      p = testdir.tmpdir.join("pytestdebug.log")
      assert "pytest_sessionstart" in p.read()
  
  def test_PYTEST_DEBUG(testdir, monkeypatch):
      monkeypatch.setenv("PYTEST_DEBUG", "1")
      result = testdir.runpytest_subprocess()
      assert result.ret == EXIT_NOTESTSCOLLECTED
      result.stderr.fnmatch_lines([
          "*pytest_plugin_registered*",
          "*manager*PluginManager*"
      ])
  
new_contents: from __future__ import absolute_import, division, print_function
  from _pytest.main import EXIT_NOTESTSCOLLECTED
  import pytest
  
  def test_version(testdir, pytestconfig):
      result = testdir.runpytest("--version")
      assert result.ret == 0
      #p = py.path.local(py.__file__).dirpath()
      result.stderr.fnmatch_lines([
          '*pytest*%s*imported from*' % (pytest.__version__, )
      ])
      if pytestconfig.pluginmanager.list_plugin_distinfo():
          result.stderr.fnmatch_lines([
              "*setuptools registered plugins:",
              "*at*",
          ])
  
  def test_help(testdir):
      result = testdir.runpytest("--help")
      assert result.ret == 0
      result.stdout.fnmatch_lines("""
          *-v*verbose*
          *setup.cfg*
          *minversion*
          *to see*markers*pytest --markers*
          *to see*fixtures*pytest --fixtures*
      """)
  
  def test_hookvalidation_unknown(testdir):
      testdir.makeconftest("""
          def pytest_hello(xyz):
              pass
      """)
      result = testdir.runpytest()
      assert result.ret != 0
      result.stdout.fnmatch_lines([
          '*unknown hook*pytest_hello*'
      ])
  
  def test_hookvalidation_optional(testdir):
      testdir.makeconftest("""
          import pytest
          @pytest.hookimpl(optionalhook=True)
          def pytest_hello(xyz):
              pass
      """)
      result = testdir.runpytest()
      assert result.ret == EXIT_NOTESTSCOLLECTED
  
  def test_traceconfig(testdir):
      result = testdir.runpytest("--traceconfig")
      result.stdout.fnmatch_lines([
          "*using*pytest*py*",
          "*active plugins*",
      ])
  
  def test_debug(testdir, monkeypatch):
      result = testdir.runpytest_subprocess("--debug")
      assert result.ret == EXIT_NOTESTSCOLLECTED
      p = testdir.tmpdir.join("pytestdebug.log")
      assert "pytest_sessionstart" in p.read()
  
  def test_PYTEST_DEBUG(testdir, monkeypatch):
      monkeypatch.setenv("PYTEST_DEBUG", "1")
      result = testdir.runpytest_subprocess()
      assert result.ret == EXIT_NOTESTSCOLLECTED
      result.stderr.fnmatch_lines([
          "*pytest_plugin_registered*",
          "*manager*PluginManager*"
      ])
  
subject: Fix test that expected "unknown hook" error on stderr