The Day TDD Started Working for Me

-
I've always agreed that Test Driven Development was a good idea and I should be doing it. But it's hard to do on top of learning new tools. And it's hard to do for GUIs. So it never quite happened.

However, after I worked with React and Redux a bit, and after doing a couple hello-world tests with Jest, it all fit together and actually made coding easier and more fun.

These were the parts that came together to make it work:
  1. Jest: Jest is included with create-react-app and is stupid-easy to start using.
  2. The Redux reducer, or functions used in the reducer, have to be pure functions and are therefore stupid-easy to test.
  3. I pulled some functions out of Redux Container mapStateToProps. These are also pure functions.
I also decided that the outputs from mapStateToProps had to have the same structure, and even use most of the same names, as the container component and all of it's child components. In other words, you could dump the data coming out of mapStateToProps and it would basically be the UI in text/outline form. No computation, restructuring, lookup, etc. were allowed.

So now the flow of events and data into the Redux store is all testable pure functions. And the flow of data almost to the UI is testable pure functions.

When all of my tests are green, anything that's broken in the browser is probably a simple typo in my JSX or something equally easy.

And now I have the advantages of TDD and can, for example, reorganize something in the shape of my Redux state and follow the change through the code by making all the newly-red tests green. That's easy. I no longer have to try to keep the Entire Structure of Everything in my head to make it all work again. Wheeee! :-)

Comments

Post a Comment

Popular posts from this blog

Callback, Promise, Observable, and Doughnuts

-
This is the story of Jerry JavaSript's Automated Slow Doughnut Shop. One day, I wanted a doughnut. So I rode my bike to the automated slow doughnut shop, where they have a slow doughnut machine. You put in a dollar. And then the machine mixes batter, heats the fat, drops the batter into the fat, lifts it out on a linked metal conveyor belt, dusts it with sugar, and drops it into your waiting hands. Once I get my doughnut, I can eat it in the usual manner. But from the time I put in my dollar until the time I receive my doughnut, I am blocked. Fortunately, the slow doughnut machine has a slot labeled, "Insert callback  here". This is great. I code up a function eatDoughnut(doughnut) . I can reference my teeth,  esophagus, stomach, and so on, because they are mine and I know all about them. And then I slip my   eatDoughnut(doughnut)  function  into the slot and get on my bike and ride  to the office while the slow doughnut machine is still mixing...
Read more

React-Redux: "Container Component" is Plumbing

-
I think I understand the pieces now... React Functional Components: Are the preferred kind of component we write in React-Redux Are functions that take a "props" object Are the preferred way to output visual stuff and wire up events The Redux Store: Has all the state which we can display Has the dispatch(action) method, which is the only way to change state Your Mission (should you choose to accept it): Use the state and the dispactch(action) function Create props which are data values needed by the functional component Create props which are event handlers that call dispatch(action) The Locations: mapStateToProps : Here you get the state and return props which are just data mapDispatchToProps : Here you get the dispatch function and return props which call it And then React-Redux's "connect" function magically combines the mapping functions and your functional component into a new component which you elsewhere. ---------------------...
Read more

box-shadow

-
box-shadow: [inset] x-offset y-offset [ blur-radius  [ spread-radius ]] [ color ] ; With all zeros, the shadow is exactly under the box. So it's hidden. The x and y offsets are like relative positioning. Take the shadow defined by any other parameters, and just move it. Blur comes first, but I'm going to talk about spread first. Spread-radius extends the shadow outward in all directions by some distance. With blur radius still set to zero, a sharp edged shadow extends outward from the box for the given distance. (It looks like a border.) For blur-radius, take a shadow with an hard edge defined according to your spread-radius. And then "fuzz" outward, putting down some color where there had been none. And fuzz inward, lightening the shadow at its old edge, and letting it darken toward it's actual color setting as you move in from . its old edge. Finally "inset" puts the shadow inside the box, instead of outside. Commas!!! Don't put co...
Read more