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Moonpig Engineering recruitment test

Welcome to the Moonpig engineering test. Here at Moonpig we really value quality code, and this test has been designed to allow you to show us how you think quality code should be written.

To allow you to focus on the design and implementation of the code we have added all the use cases we expect you to implement to the bottom of the instructions. In return we ask that you make sure your implementation follows all the best practices you are aware of, and that at the end of it, the code you submit, is code you are proud of.

We have not set a time limit, we prefer that you spend some extra time to get it right and write the highest quality code you can. Please feel free to make any changes you want to the solution, add classes, remove projects etc.

We are interested in seeing how you approach the task so please commit more regularly than you normally would so we can see each step and include the .git folder in your submission.

When complete please upload your solution and answers in a .zip to the google drive link provided to you by the recruiter.

Programming Exercise - Moonpig Post Office

You have been tasked with creating a service that calculates the estimated despatch dates of customers' orders.

An order consists of an order date and a collection of products that a customer has added to their shopping basket.

Each of these products is supplied to Moonpig on demand through a number of 3rd party suppliers.

As soon as an order is received by a supplier, the supplier will start processing the order. The supplier has an agreed lead time in which to process the order before delivering it to the Moonpig Post Office.

Once the Moonpig Post Office has received all products in an order it is despatched to the customer.

Assumptions:

  1. Suppliers start processing an order on the same day that the order is received. For example, a supplier with a lead time of one day, receiving an order today will send it to Moonpig tomorrow.

  2. For the purposes of this exercise we are ignoring time i.e. if a supplier has a lead time of 1 day then an order received any time on Tuesday would arrive at Moonpig on the Wednesday.

  3. Once all products for an order have arrived at Moonpig from the suppliers, they will be despatched to the customer on the same day.

Part 1

When the /api/DespatchDate endpoint is hit return the despatch date of that order.

Part 2

Moonpig Post Office staff are getting complaints from customers expecting packages to be delivered on the weekend. You find out that the Moonpig post office is shut over the weekend. Packages received from a supplier on a weekend will be despatched the following Monday.

Modify the existing code to ensure that any orders received from a supplier on the weekend are despatched on the following Monday.

Part 3

The Moonpig post office is still getting complaints... It turns out suppliers don't work during the weekend as well, i.e. if an order is received on the Friday with a lead time of 2 days, Moonpig would receive and despatch on the Tuesday.

Modify the existing code to ensure that any orders that would have been processed during the weekend resume processing on Monday.

Parts 1 & 2 have already been completed albeit lacking in quality. Please review the code, document the problems you find (see question 1), and refactor into what you would consider quality code.

Once you have completed the refactoring, extend your solution to capture the requirements listed in part 3.

Please note, the provided DbContext is a stubbed class which provides test data. Please feel free to use this in your implementation and tests but do keep in mind that it would be switched for something like an EntityFramework DBContext backed by a real database in production.

While completing the exercise please answer the questions listed below. We are not looking for essay length answers. You can add the answers in this document.

Questions

Q1. What 'code smells' / anti-patterns did you find in the existing implementation of part 1 & 2?

Q2. What best practices have you used while implementing your solution?

Q3. What further steps would you take to improve the solution given more time?

Q4. What's a technology that you're excited about and where do you see this being applicable? (Your answer does not have to be related to this problem)

Request and Response Examples

Please see examples for how to make requests and the expected response below.

Request

The service is setup as a Web API and takes a request in the following format

GET /api/DespatchDate?ProductIds={product_id}&orderDate={order_date}

e.g.

GET /api/DespatchDate?ProductIds=1&orderDate=2018-01-29T00:00:00
GET /api/DespatchDate?ProductIds=2&ProductIds=3&orderDate=2018-01-29T00:00:00

Response

The response will be a JSON object with a date property set to the resulting Despatch Date

{
    "date" : "2018-01-30T00:00:00"
}

Acceptance Criteria

Lead time added to despatch date

Given an order contains a product from a supplier with a lead time of 1 day
And the order is place on a Monday - 01/01/2018
When the despatch date is calculated
Then the despatch date is Tuesday - 02/01/2018

Given an order contains a product from a supplier with a lead time of 2 days
And the order is place on a Monday - 01/01/2018
When the despatch date is calculated
Then the despatch date is Wednesday - 03/01/2018

Supplier with longest lead time is used for calculation

Given an order contains a product from a supplier with a lead time of 1 day
And the order also contains a product from a different supplier with a lead time of 2 days
And the order is place on a Monday - 01/01/2018
When the despatch date is calculated
Then the despatch date is Wednesday - 03/01/2018

Lead time is not counted over a weekend

Given an order contains a product from a supplier with a lead time of 1 day
And the order is place on a Friday - 05/01/2018
When the despatch date is calculated
Then the despatch date is Monday - 08/01/2018

Given an order contains a product from a supplier with a lead time of 1 day
And the order is place on a Saturday - 06/01/18
When the despatch date is calculated
Then the despatch date is Tuesday - 09/01/2018

Given an order contains a product from a supplier with a lead time of 1 days
And the order is place on a Sunday - 07/01/2018
When the despatch date is calculated
Then the despatch date is Tuesday - 09/01/2018

Lead time over multiple weeks

Given an order contains a product from a supplier with a lead time of 6 days
And the order is place on a Friday - 05/01/2018
When the despatch date is calculated
Then the despatch date is Monday - 15/01/2018

Given an order contains a product from a supplier with a lead time of 11 days
And the order is place on a Friday - 05/01/2018
When the despatch date is calculated
Then the despatch date is Monday - 22/01/2018