Difference between revisions of "Python-3.4.3/C4/Testing-and-Debugging/English"

Objectives

• Understand what is software testing
• Test simple functions for their functionality
• Automate tests
• Understand the need for coding style and
• Learn some of the standards followed by the Python Community

System Specifications

• Ubuntu Linux 16.04 operating system
• Python 3.4.3
• IPython 5.1.0 and
• Gedit text editor

Prerequisite

If not, see the relevant Python tutorials on this website.

Software Testing

Software testing is the process to evaluate the functionality of a software or a program.

It helps to find whether the program met the specified requirements or not.

It ensures a defect free program so that we will get a quality program.

Source code

You should download in the current working directory and use them.

def gcd(a, b): if b == 0: return a return gcd(b, a%b)

Highlight def gcd(a,b):

This is a simple function to calculate gcd of two numbers.

We need a set of inputs for the variable a and b.

if __name__ == '__main__':

result = gcd(48, 64)

if result != 16:

print("Test failed")

print("Test Passed")

For this test case we know that the GCD is 16.

So that is the expected output.

python3 test_gcd.py

Open the terminal and type

python3 test underscore gcd.py

We get the output as Test Passed' which means our code is correct.

This is where the concept of automating tests comes in.

Open the file textcases.txt where the various testing parameters are given.

12 28 4

18 36 18

4678 39763 2339

The third parameter is the correct output result.

We have separated the elements by a space.

from find_gcd import gcd

if __name__ == '__main__':

for line in open('testcases.txt'):

numbers = line.split()

x, y = int(numbers[0]) , int(numbers[1])

result = int(numbers[2])

if gcd(x, y) != result:

print ("Failed gcd test for", x, y)

else:

print ("Test passed", result)

Next the testcases.txt file is read line by line.

The first two input parameters are assigned to the variables x and y.

The third parameter which is the correct output value is assigned to the variable result.

We check whether the value returned by the gcd function is equal to the value in the variable result.

Finally it prints the message accordingly.

python3 automate_test_gcd.py

python3 automate underscore test underscore gcd.py

The value calculated by the gcd function is equal to the output value provided in the testcases.txt.

Try this exercise and then resume the video.

Assignment 1

Use the data from the file lcmtestcases.txt

Open lcmtestcases.txt

The file name is find underscore lcm.py

This is the data file for the lcm test cases.

This file name is lcmtestcases.txt

Note that both these files should be in the current working directory.

Let us now run the script and test our code.

[Terminal]

python3 find_lcm.py

Because the corresponding input in lcmtestcases.txt is incorrect.

This is to check the behavior of the program on incorrect conditions.

Coding Style

• A good program should be readable.
• So others can extend and improve it.
• Code is read more often than it is written.

Meaningful names

As we can see in the example, it is very easy to understand what the code is doing.

Proper naming helps so much in understanding the code.

Coding Instructions

• Four Space Indentation
• 79 characters limit on a line
• Functions and methods should be separated with two blank lines.

Code Instructions

• Use whitespace around operators and after punctuations.

Summary

In this tutorial, we have learnt to,

• Create simple tests for a function
• Automate tests using many predefined test cases and
• Use python coding standards.

Self assessment questions

1. What is the proper indentation for python code according to the style guidelines?

1. Four Space Indentation is required for writing a python code according to the style guidelines.

Acknowledgment

http://spoken-tutorial.org

For more details, visit this website.

Thanks for watching.