text: var shell = require('..');
  
  var assert = require('assert'),
      fs = require('fs');
  
  shell.config.silent = true;
  
  shell.rm('-rf', 'tmp');
  shell.mkdir('tmp');
  
  //
  // Invalids
  //
  
  shell.sed();
  assert.ok(shell.error());
  
  shell.sed(/asdf/g); // too few args
  assert.ok(shell.error());
  
  shell.sed(/asdf/g, 'nada'); // too few args
  assert.ok(shell.error());
  
  assert.equal(fs.existsSync('/asdfasdf'), false); // sanity check
  shell.sed(/asdf/g, 'nada', '/asdfasdf'); // no such file
  assert.ok(shell.error());
  
  //
  // Valids
  //
  
  shell.cp('-f', 'resources/file1', 'tmp/file1');
  var result = shell.sed('test1', 'hello', 'tmp/file1'); // search string
  assert.equal(shell.error(), null);
  assert.equal(result, 'hello');
  
  var result = shell.sed(/test1/, 'hello', 'tmp/file1'); // search regex
  assert.equal(shell.error(), null);
  assert.equal(result, 'hello');
  
  var result = shell.sed(/test1/, 1234, 'tmp/file1'); // numeric replacement
  assert.equal(shell.error(), null);
  assert.equal(result, '1234');
  
  var result = shell.sed('-i', /test1/, 'hello', 'tmp/file1');
  assert.equal(shell.error(), null);
  assert.equal(result, 'hello');
  assert.equal(shell.cat('tmp/file1'), 'hello');
  
  shell.exit(123);
  