text: """Unit tests for the FileChecker class."""
  from unittest import mock
  
  import pytest
  
  import flake8
  from flake8 import checker
  
  
  @mock.patch('flake8.processor.FileProcessor')
  def test_run_ast_checks_handles_SyntaxErrors(FileProcessor):  # noqa: N802,N803
      """Stress our SyntaxError handling.
  
      Related to: https://github.com/pycqa/flake8/issues/169
      """
      processor = mock.Mock(lines=[])
      FileProcessor.return_value = processor
      processor.build_ast.side_effect = SyntaxError('Failed to build ast',
                                                    ('', 1, 5, 'foo(\n'))
      file_checker = checker.FileChecker(__file__, checks={}, options=object())
  
      with mock.patch.object(file_checker, 'report') as report:
          file_checker.run_ast_checks()
  
          report.assert_called_once_with(
              'E999', 1, 3,
              'SyntaxError: Failed to build ast',
          )
  
  
  @mock.patch('flake8.checker.FileChecker._make_processor', return_value=None)
  def test_repr(*args):
      """Verify we generate a correct repr."""
      file_checker = checker.FileChecker(
          'example.py', checks={}, options=object(),
      )
      assert repr(file_checker) == 'FileChecker for example.py'
  
  
  def test_nonexistent_file():
      """Verify that checking non-existent file results in an error."""
      c = checker.FileChecker("foobar.py", checks={}, options=object())
  
      assert c.processor is None
      assert not c.should_process
      assert len(c.results) == 1
      error = c.results[0]
      assert error[0] == "E902"
  
  
  def test_raises_exception_on_failed_plugin(tmp_path, default_options):
      """Checks that a failing plugin results in PluginExecutionFailed."""
      foobar = tmp_path / 'foobar.py'
      foobar.write_text("I exist!")  # Create temp file
      plugin = {
          "name": "failure",
          "plugin_name": "failure",  # Both are necessary
          "parameters": dict(),
          "plugin": mock.MagicMock(side_effect=ValueError),
      }
      """Verify a failing plugin results in an plugin error"""
      fchecker = checker.FileChecker(
          str(foobar), checks=[], options=default_options)
      with pytest.raises(flake8.exceptions.PluginExecutionFailed):
          fchecker.run_check(plugin)
  