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HOW TO: Correctly stub stdout

Craig Taub edited this page Jun 17, 2019 · 2 revisions

If you want to stub stdout inside your own code (via process.stdout.write or console.log) there is a potential to hinder Mochas reporters output. This is because they rely on the same mechanisms to print results of the tests.

i.e.

it('should do, but it do not', function() {
  // user wants to hide output generated by console.log calls in fn 'foo'
  console.log = function() {};
  foo();

  expect(...)
});

This will result in a faulty reporter output.

The correct way to handle this is to stub before and restore after the function call.

it('will do', function() {
  var consoleLogStub = sinon.stub(console, 'log');
  foo();
  consoleLogStub.restore();

  expect(...)
});

Now the reporters can run and print the assertion without any interference, while stubbing stdout inside your function.