“Tests are something you know you should be doing, but haven’t had the time to learn, or tried to and didn’t get very far.”

Intro

Objective

1. To know what exactly is unit testing, to know about its applications and to write some tests live(if time allows)
2. Introduction to what’s linting and how you can extend it to your favourite text editor
3. Auto Formatters and naming conventions
4. All examples shown using Python

Libraries used

1. unittest (python inbuilt)
2. math (python inbuilt)
3. flake8 (linter)
4. yapf (auto formatter)

UnitTesing in Python

Start a project called areas

Directory Structure

areas
     ├── areas
     │   ├── area.py
     │   └── __init__.py
     └── tests
         └── __init__.py

Creation of directories and files

mkdir -p areas/{areas,tests}
cd areas
touch areas/__init__.py areas/area.py tests/__init__.py

Create a function for finding area of circle

from math import pi
def circle_area(r):
    return pi * (r**r)

Run with sample values

radii = [0,1,0.1,2+3j,-7,True,'a']
for radius in radii:
    print(circle_area(radius))

Are all the radii valid?

Are negative values valid?

No. Since radii here are simply the value of distance from center of circle to its circumference. Thus it should be +ve.

Are data types other than int and float valid?

No. It doesn’t make any sense to give radius as True or as String.

Solution : Proper UnitTesting

Start by importing the necessary modules

import unittest
from math import pi
from areas import area

Subclass unittest.TestCase and create appropriate tests

class TestCircleArea(unittest.TestCase):

Create a test to assert value of area function for different radii

Different Assert Methods

def test_radius(self):
    result = area.circle_area(1)
    self.assertEqual(result,pi)

If the test outputs OK then our function definition is correct

Create a test to check negative values

We can raise ValueError on intercepting a negative value as radius

"""
in test file
"""
def on_negative_radii(self):
    self.assertRaises(ValueError,area.circle_area,-7)

"""
in area file, inside circle_area function, add the following
"""
if r<0:
   raise ValueError

Create a test to check for invalid data types

We can raise TypeError on intercepting a invalid datatype value

"""
in test file
"""
def on_other_types(self):
    self.assertRaises(TypeError,area.circle_area,"Hello")

"""
in area file, inside circle_area function, add the following
"""
if type(r) not in [int,float]:
   raise TypeError

Workout Problem

Create an unittest, which can be used with all programs done using Python Sockets, in Computer Networks Lab

Example : Most people manually set the IP Address of the system while creating a socket. So when changing the system, the ip will also change, and will have to be manually changed again. Write a test case to make sure the IP Address is always same as that of the system.

Linting

What’s it?

It’s the process of automatically checking the program code for errors

How can it be done?

via your editor(live linting)

via your build process

via pre-commit hooks in version control

Types of Linting

Syntax

Refers to the anti-patterns and missing of keywords etc in code

Code Style

It deals with enforcing proper naming convention and standards

Popular linters

Language	Linter
C	Clangd
C++	Clangd/CppCheck
Python	Flake8/Pylint
Java	CheckStyle
Shell Script	Shellcheck

Auto Formatting

What’s it?

It’s the process of automatically formatting the code to follow a particular style guide and coding convention

Why do we need to use it?

Enforcing common style guide is valuable while in a project with team

Code gets formatted with click of a button or command

No need to discuss style in code review

Saves time and energy

Popular formatters

Language	Formatter
C	Clang-Format
C++	Clang-Format
Python	Yapf/Black
Java	Google-Java-Format

Coding Standards and Style Guide

view the file pep8-coding-standards

or visit pep8 org