Grocery Store

At a Glance

• Individual, stage 2 project
• Due before class, Mon., Aug 26

Learning Goals

Skills that should be demonstrated through this project:

• Test-Driven-Development
• Using instance variables and methods
• Object composition
• Reading data from a CSV file

Objective

We want to write library code that grocery stores would use. We want our library code to be able to keep track of the orders that folks make in the store.

Getting Started

1. Fork the project master.
2. Clone the forked repo: $ git clone [YOUR FORKED REPO URL]
3. cd into the dir created $ cd grocery-store
4. Run gem install minitest-skip to install an extra gem for testing (more on what this actually does later).

Tests

This is the first project where you'll be writing your own tests. Following the instructions from the TDD lecture, there are three things in our project directory:

Rakefile
lib/
specs/

Each class you write should get its own file, lib/class_name.rb. The specs for that class will be in specs/class_name_spec.rb, and you can run all specs using the rake command from your terminal.

Implementation Requirements

Wave 1

Wave 1 Goals

• Create a class
• Write instance methods inside a class to perform actions
• Link two classes using composition
• Use exceptions to handle errors
• Verify code correctness by testing

Testing Requirements in Wave 1

For Wave 1, all tests have been provided for you. For each piece of functionality that you build, you should run the tests from the command line using the rake command. To focus on only one test at a time, change all it methods to xit except for the one test you'd like to run. All tests provided should be passing at the end of your work on Wave 1.

Customer Implementation Requirements

Create a class called Customer. Each new Customer should include the following attributes:

• ID, a number
• Email address, a string
• Delivery address, a hash

ID should be readable but not writable; the other two attributes can be both read and written.

Order Implementation Requirements

Create a class called Order. Each new Order should include the following attributes:

• ID, a number (read-only)
• A collection of products and their cost. This data will be given as a hash that looks like this:

  { "banana" => 1.99, "cracker" => 3.00 }

  • Zero products is permitted (an empty hash)
  • You can assume that there is only one of each product
• An instance of Customer, the person who placed this order
• A fulfillment_status, a symbol, one of :pending, :paid, :processing, :shipped, or :complete
  • If no fulfillment_status is provided, it will default to :pending
  • If a status is given that is not one of the above, an ArgumentError should be raised

In addition, Order should have:

• A total method which will calculate the total cost of the order by:
  • Summing up the products
  • Adding a 7.5% tax
  • Rounding the result to two decimal places
• An add_product method which will take in two parameters, product name and price, and add the data to the product collection
  • If a product with the same name has already been added to the order, an ArgumentError should be raised

Optional Enhancements

Make sure to write tests for any optionals you implement!

• Add a remove_product method to the Order class which will take in one parameter, a product name, and remove the product from the collection
  • If no product with that name was found, an ArgumentError should be raised

Wave 2

Wave 2 Goals

• Create and use class methods
• Use a CSV file for loading data
• Create your own tests to verify method correctness

Testing Requirements in Wave 2

You enter Wave 2 with all tests from Wave 1 passing. In Wave 2, all the tests for Customer and one of the specs for Order have been provided. The remaining tests are stubbed out in order_spec.rb. Filling in these stubs is part of Wave 2.

When you are done with Wave 2, all your tests from Wave 1 should still pass!

Required Customer Updates

Add the following class methods to the Customer class:

• self.all - returns a collection of Customer instances, representing all of the Customer described in the CSV file
• self.find(id) - returns an instance of Customer where the value of the id field in the CSV matches the passed parameter

Customer.find should not parse the CSV file itself. Instead it should invoke Customer.all and search through the results for a customer with a matching ID.

Customer CSV File

Customer data lives in the file data/customers.csv. The data in this file has the following columns:

Field	Type	Description
Customer ID	Integer	A unique identifier corresponding to the Customer
Email	String	The customer's e-mail address
Address 1	String	The customer's street address
City	String	The customer's city
State	String	The customer's state
Zip Code	String	The customer's zip code

Note: The columns in the CSV file don't quite match the parameters for the constructor. You'll need to do some work

Error Handling

What should your program do if Customer.find is called with an ID that doesn't exist? Hint: what does the find method for a Ruby array do?

Required Order Updates

Add the following class methods to the Order class:

• self.all - returns a collection of Order instances, representing all of the Orders described in the CSV file
• self.find(id) - returns an instance of Order where the value of the id field in the CSV matches the passed parameter

As before, Order.find should call Order.all instead of loading the CSV file itself.

Order CSV File

Order data lives in the file data/orders.csv. The data in this file has the following columns:

Field	Type	Description
ID	Integer	A unique identifier for that Online Order
Products	String	The list of products in the following format: name:price;nextname:nextprice
Customer ID	Integer	A unique identifier corresponding to a Customer
Status	String	A string representing the order's current status

The data in this file is very different than what Order.new takes. You will have two big pieces of work here:

1. Parse the list of products into a hash
   • This would be a great piece of logic to put into a helper method
   • You might want to look into Ruby's split method
   • We recommend manually copying the first product string from the CSV file and using pry to prototype this logic
2. Turn the customer ID into an instance of Customer
   • Didn't you just write a method to do this?

Optional Enhancements

• Order.find_by_customer(customer_id) - returns a list of Order instances where the value of the customer's ID matches the passed parameter.

Optional Wave 3: Saving Order Data

Add a new class method to each of Order and Customer called save. The save method should take one parameter, a file name, and save the list of objects to that file in the same format as the original CSV file.

When you're done, you should be able to write code like the following:

$ pry -r ./lib/customer.rb
pry> Customer.save('new_customer_list.csv')
pry> exit
$ cat new_customer_list.csv
1,[email protected],71596 Eden Route,Connellymouth,LA,98872-9105
2,[email protected],876 Kemmer Cove,East Luellatown,AL,21362
[ ... ]

We do not require testing for this wave - testing with external resouces like files is tricky to get right. Instead, do some brainstorming: what kind of things would tests need to do, and what error cases would they handle? Why is testing tricky, and what might be done to overcome these problems? How could you learn more about this?

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