it("can tell you if a testdouble object was called", function() {
  var td = testdouble.function();
  td();
  expect(td).to.have.been.called;  // instead of `verify(td)`!
});

it("can tell you if a testdouble object was called a certain way", function() {
  var td = testdouble.function();
  td("hi");
  expect(td).to.have.been.calledWith("hi");  // instead of `verify(td("hi"))`!
});

// at the top of a test file or in a test helper
var td = require("testdouble");
var chai = require("chai");
var tdChai = require("testdouble-chai");
chai.use(tdChai(td)); // make sure to call tdChai with td to inject the dependency