// async() returns done callback
test(..., function(assert) {
  // async() can be invoked multiple times, each callback has to be invoked
  var done = assert.async();
  setTimeout(function() {
    done();
  });
});
// this makes integration of Promises very easy
test( ..., function( assert ) {
    /* ... */
    APP.foo().always( assert.async() ).done( function () {
        assert.ok(true);
    } );
    APP.bar().always( assert.async() ).done( function () {
        assert.ok(true);
    } );
});

// all tests are async, always have to explicitly end the test, async or not
test(..., function(assert) {
  assert.end();
});

// expect sets up async test, finishes when number of assertions ran
test(..., function(assert) {
  // makes this test async
  expect(1);
  setTimeout(function() {
    // expected 1 assertion, continue with other tests
    // any other assertions will fail this test
    assert.ok(true);
  });

// return a promise from the test
[...]