In synchronous tests, both describe and it statements are executed in the order they are laid out.

Test Foo should run before Bar:

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describe('Suite', function () {
  it('Foo', function () {
  });
  it('Bar', function () {
  });
});

Suite Foo should run before Bar:

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describe('Foo', function () {
});
describe('Bar', function () {
});

In asynchronous tests, the same ordering applies.

Test Foo should run before Bar even Foo takes much longer to execute, and Suite B should also run after Suite A:

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var should = require('should');
describe('Suite A', function () {
  it('Foo', function (done) {
    setTimeout(function () {
      (true).should.equal(true);
      done();
    }, 1000);
  });
  it('Bar', function () {
    (true).should.equal(true);
  });
});
describe('Suite B', function () {
  it('Foo', function () {
    (true).should.equal(true);
  });
});

Result:

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Suite A
  ✓ Foo (1002ms)
  ✓ Bar 
Suite B
  ✓ Foo 
3 passing (1s)

This is the great feature in Mocha.

In Node v0.10.x, the console functions are synchronous when the destination is a terminal or a file (to avoid lost messages in case of premature exit) and asynchronous when it’s a pipe (to avoid blocking for long periods of time). See console. We can test it with the following script: