add test for no callback error

test/unit/nodeify-test.js

@@ -17,4 +17,15 @@ describe('nodeify', function () {
       done()
     })
   })
+
+  it('should throw if the last argument is not a function', function (done) {
+    var nodified = nodeify(obj.promiseFunc, obj)
+    try {
+      nodified('baz')
+      done(new Error('should have thrown if the last argument is not a function'))
+    } catch (err) {
+      if (err.message === 'callback is not a function') done()
+      else done(err)
+    }
+  })
 })