code: function SpyConstructor (opts) {
      Constructor.call(this, opts)
  
      // Spy on Constructor functions
      for (var key in this) {
        if (this[key] instanceof Function) {
          this[key] = sinon.spy(this[key])
        }
      }
  
      SpyConstructor.instances.push(this)
    }
docs: Wrap methods with spies and store instances