lab02 : Coffee Shop

In this lab, we’ll utilize inheritance functionality and define various Beverage objects and its properties. You’ll have the opportunity to practice:

• Defining a base class and creating an inheritance hierarchy
• Defining derived classes and inheriting data and reusing functionality from a base class
• Overriding inherited methods from the parent class in the derived classes
• Installing pytest and unit testing your code

Note: In general, it is always important to work on labs and reading early so you can gain the proper context and utilize our office hours to seek assistance / ask clarifying questions during the weekdays before the deadline if needed!

It may be a good idea to read up on some concepts we’ll be using in this lab before you get started, specifically Chapter 1.4.6.2 (Inheritance).

In this lab, we will create a Beverage base class as well as defining specific classes for a couple types of Beverages (Coffee and FruitJuice). The DrinkOrder class will organize Beverages and will provide a summary of a specific drink order.

In addition to defining classes for various Beverages and a Drink Order, you will test your code for correctness by unit testing various scenarios using pytest.

Instructions

You will need to create five files:

• Beverage.py - file containing a class definition with attributes all Beverages have.
• Coffee.py - file containing a class definition of a coffee beverage that inherits from the Beverage class.
• FruitJuice.py - file containing a class definition of a fruit juice beverage that inherits from the Beverage class.
• DrinkOrder.py - file containing a class definition of a customer’s drink order containing organizing various beverages.
• testFile.py - file containing pytest functions testing the Beverage, Coffee, FruitJuice, and DrinkOrder classes.

There will be no starter code for this assignment, but rather the class descriptions and required methods are defined in the specification below.

It’s recommended that you organize your lab work in its own directory. This way all files for a lab are located in a single folder. Also, this will be easy to import various files into your code using the import / from technique shown in lecture.

Beverage class

The Beverage.py file will contain the class definition of what a general beverage is.

We will define this class’ attributes as follows:

• ounces - positive int that represents the number of ounces of the beverage.
• price - positive float that represents the price of the beverage.

You should write a constructor that passes in values for all the fields. You may assume calls to the constructor will always contain a positive int representing the beverage’s ounces and a positive float representing the beverage’s price.

• __init__(self, ounces, price)

In addition to your constructor, your class definition should also support “setter” and “getter” methods that can update and retrieve the state of the Beverage objects:

• updateOunces(self, newOunces) - updates the ounces of the beverage
• updatePrice(self, newPrice) - updates the price of the beverage
• getOunces(self) - returns the ounces of the beverage
• getPrice(self) - returns the price of the beverage

Each Beverage object should be able to call a method getInfo(self) that you will implement, which returns a str with the current beverage’s ounces and price. Since there are many beverages, the following output represents what will be returned if we call the getInfo method after constructing a Beverage object:

b1 = Beverage(16, 20.5)
print(b1.getInfo())

Output:

16 oz, $20.50

Note: The b1.getInfo() return value in the example above does not contain a newline character (\n) at the end.

Tip: Note that the return string will contain a price with two decimal places (as traditionally used when displaying prices). Consider using the string’s format method have floating point values contain 2 decimal places. For example:

>>> price = 1.5
>>> "{:.2f}".format(price)
'1.50'

You can refer to CS 8 lecture notes on string formatting if you would like a review https://ucsb-cs8.github.io/m19-wang/lectures/lect11/

Coffee class

The Coffee.py file will contain the class definition of what a coffee beverage will have. Since a coffee IS-A beverage, we will inherit the values we defined in the Beverage class.

Your Coffee class definition should support the following constructor and method:

• __init__(self, ounces, price, style) - constructor that extends the parent class’ (Beverage) constructor and sets the style of coffee (for example, Cappuccino, Americano, Espresso, etc.) as an attribute to the Coffee class. Note, you may assume the style parameter is a str. In order to avoid code duplication, you must explicitly utilize the base class’ constructor to set the ounces and price attributes.
• getInfo(self) - method that overrides the inherited getInfo method in the Beverage class, and returns a str with the properties of a Coffee object. In order to avoid code duplication, you must explicitly utilize the base class’ getInfo method to construct the Coffee object’s information. An example of what the return string format of the getInfo method is shown below:

>>> c1 = Coffee(8, 3.0, "Espresso")
>>> c1.getInfo()
'Espresso Coffee, 8 oz, $3.00'

Note: The c1.getInfo() return value in the example above does not contain a newline character (\n) at the end.

FruitJuice class

The FruitJuice.py file will contain the class definition of what a fruit juice beverage will have. Since a fruit juice IS-A beverage, we will inherit the values we defined in the Beverage class.

Your FruitJuice class definition should support the following constructor and method:

• __init__(self, ounces, price, fruits) - constructor that extends the parent class’ (Beverage) constructor and sets a list of fruits used in this fruit juice object. Note, you may assume the fruits parameter is a list of strings representing the types of fruits (for example, "orange", "blueberry", "guava", etc.) used in the fruit juice. In order to avoid code duplication, you must explicitly utilize the base class’ constructor to set the ounces and price attributes.
• getInfo(self) - method that overrides the inherited getInfo method in the Beverage class, and returns a str with the properties of a FruitJuice object. In order to avoid code duplication, you must explicitly utilize the bass class getInfo method to construct the FruitJuice object’s information. An example of what the return string format of the getInfo method is shown below:

>>> juice = FruitJuice(16, 4.5, ["Apple", "Guava"])
>>> juice.getInfo()
'Apple/Guava Juice, 16 oz, $4.50'

Note: The juice.getInfo() return value in the example above does not contain a newline character (\n) at the end.

DrinkOrder class

The DrinkOrder.py file will contain the class definition of what a customer’s drink order will contain along with the total price of all beverages in the drink order.

Your DrinkOrder class definition should support the following constructor and methods:

• __init__(self) - constructor that initializes an empty list to the class. Name this list attribute drinks. This list drinks will eventually expand with beverages for the customer’s drink order.
• addBeverage(self, beverage) - method that will add the beverage parameter to the DrinkOrder’s list. The most recently added beverage will exist at the end of the list. You may assume the beverage parameter will either be a FruitJuice or Coffee object.
• getTotalOrder(self) - method that will return a str containing each beverage in the drink order, and the total price of all beverages in the drink order. An example of what the return string format of the getTotalOrder method is shown below:

c1 = Coffee(8, 3.0, "Espresso")
juice = FruitJuice(16, 4.5, ["Apple", "Guava"])
order = DrinkOrder()
order.addBeverage(c1)
order.addBeverage(juice)
print(order.getTotalOrder())

Output:

Order Items:
* Espresso Coffee, 8 oz, $3.00
* Apple/Guava Juice, 16 oz, $4.50
Total Price: $7.50

An example of what the return string format of the getTotalOrder method when there are no beverages in the Drink Order is shown below:

Order Items:
Total Price: $0.00

Note: The order.getTotalOrder() return value in the examples above do not contain a newline character (\n) at the end.

testFile.py pytests

This file will contain unit tests using pytest to test if your functionality is correct. You should create your own tests different than the examples given in this writeup. Think of various scenarios and method calls to be certain that the state of your objects and return values are correct (provide enough tests such that all method calls in Beverage, Coffee, and FruitJuice and DrinkOrder are covered). Even though Gradescope will not use this file when running the automated tests, it is important to provide this file with various test cases (testing is important!!). We will manually grade your testFile.py to make sure your unit tests cover the defined methods in Beverage, Coffee, and FruitJuice and DrinkOrder. There are many ways to organize your test functions - my recommendation is writing a test for each class, and calling various methods to make sure the functionality and state of the objects are correct.

Pytest will need to be installed on your computer since it does not come with Python by default. Some links for you to use when installing pytest are:

• Installation Guide: https://docs.pytest.org/en/stable/getting-started.html
  • Note: on MacOS running Python3, try using pip3 instead of pip if your installation is not working.
• Windows Installation Guide (created by previous Learning Assistants): Python and Pytest Installation Guide for Windows
  • If you have installed Python on your windows machine already without selecting Add Python 3.x to PATH, the easiest thing to do is uninstall / reinstall Python and be sure to select this box.

In order to run your pytests, you can navigate to your folder where your lab02 code is located with the command line interface, and run:

On Mac:

python3 -m pytest testFile.py

On Windows:

python -m pytest testFile.py

• If you run into any difficulties when installing / running pytest, and/or have any questions about testing your code, we will be happy to help you out during our office / lab hours!

Submission

Once you’re done with writing your class definition and tests, Submit your Beverage.py, Coffee.py, FruitJuice.py, DrinkOrder.py, and testFile.py files to the Lab02 assignment on Gradescope. There will be various unit tests Gradescope will run to ensure your code is working correctly based on the specifications given in this lab.

Note on grading for labs with testing component: For this lab assignment (and all lab assignments requiring a testFile.py), we will only manually grade the tests you write. In general, your lab score will be based on the autograder’s score (out of 100 points).

• If you write your tests correctly according to the specifications, then you will receive 100/100 points.
• If your written tests are missing, incomplete, or incorrect, then there will be up to a 10 point deduction from the autograder score. For example, if you didn’t write any tests, then your lab score will be 90/100 (-10 point deduction from the autograder’s score).

If Gradescope’s tests don’t pass, you may get some error message that may or may not be obvious. Don’t worry - if the tests didn’t pass, take a minute to think about what may have caused the error. Try to think of your pytests and see if you can write a test to help you debug the error (if you haven’t already). If you’re still not sure why you’re getting the error, feel free to ask your TAs or Learning Assistants.