dmngu9/traffic-system

SafetyCulture take home assignment - implementing traffic light intersection simulation

traffic-system

SafetyCulture take home assignment - implementing traffic light intersection simulation

Requirements

Simulation time is 30 mins Light change from Green to Red or vice versa takes 5 mins. Prior turning Red, The light should display Yellow for 30 seconds

How to Start

Make sure NodeJs is installed first (I used Nodejs v6).

Must install dev-dependencies first, run npm install

To build project, run npm start. Open the index.html in browser

To run unit tests, run npm test

To check typescript linting, run npm run checkLinting

Design

There 4 traffic lights at positions: North, South, East, West. North & South traffic lights follow the same pattern and so do East & West traffic lights. I indentify 4 possible state as shown in the diagram below.

The design that i came up with is displayed in the UML graph below.

In the design, the state name follows this rule: signal of N/S traffic light combined with E/W traffic light signal. For example GreenRedState (N/S is Green and E/W is Red).

I made an assumption that the state change cycle always start at GreenRedState. When simulation finished, it will reset back to that state.

I have not taken into account if there are extra light (the one with arrow simple) for turning or queue of vehicles on the road. If this was included, the UML design would have much more complex and there is no way I can do that in 5 hrs.

Things that I have not done properly

Karma source map is not configured correctly. No line number shows for what expect statement fails in the test.

Karma coverage always show 100%. Not sure what is going on there. I set up coverage with Istanbul at work and it works fine.

Using Webpack for small project is overkill. I need ts-loader in order to load CommonJs to browser. Other option is to use Browserify but Im not familiar with it.

TrafficLight class takes UI Element and anything relate to UI Element is not tested in unit tests. I feel like this is more like e2e tests.

The init and destroy of StateMachine is very basic. It might be a weakness for scaling application.

I wonder if my code is type strong or not