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{{{ Show the "Title" slide }}} Hello friends and welcome to the tutorial on, 'Getting started with TDD'
{{{ Show "Objectives" slide }}}

At the end of this tutorial, you will be able to,

  1. Understand basics of Test Driven Development.
  2. Understand the use test cases.
  3. Write simple tests for a function.
{{{ Switch the "Pre-requisite" slide }}} Before beginning this tutorial, we would suggest you to complete the tutorial on "Getting started with functions".
{{{ show "What is TDD?" slide }}}

Test-driven development is a software development process that relies on the repetition of a very short development cycle.

The basics of Test Driven Development are,

  1. Decide the new feature you want to implement & the methodology to test it.
  2. Write tests for the new feature decided upon.
  3. Just write enough code so that the test can run, but, it fails.
{{{ show "What is TDD?.." slide }}}
  1. Modify the code so that all the current tests & the previous tests pass.
  2. Run tests to see if all the tests pass successfully.
  3. Refactor the code - optimize the algorithm, remove duplication & documentation, etc.
  4. And finally run the tests again to see if all the tests pass.
{{{ show "First test - fibonacci" slide }}} To illustrate TDD, lets take a simple program. Consider a function "fibonacci", that takes one argument and returns the nth number of fibonacci series. As shown in the example, c will contain the 3rd digit of the fibonacci series that starts counting from 0(zero).
{{{ show "Test Cases" slide }}} To test any function it is important to have enough test cases & their expected outputs before you start writing the test cases. Test cases are expected outputs for a given set of inputs. So, to test fibonacci function, we need test cases. As shown in this slide, our test cases are, when 'n=3', '2' is the expected output from the fibonnaci series. Similarly, when 'n=4', '3' is the expected output. Test cases can either be true or false depending on their actual behaviour against the expected behaviour.
{{{ show "Test cases-Code" slide }}} The sample code for test cases is shown here. Observe that if any "if" statement is executed, test aborts after printing the error message.
{{{ show the "Stubs" slide }}} Now, the fibonacci function is written just enough so that the tests can run. But, obviously the tests are going to fail.
{{{ show "fibonacci.py" slide }}} We will now combine the fibonnaci stub function we just wrote & the test cases together in "fibonacci.py" file. Note that the test cases should be added after "name=main" idiom.
{{{ show the "first run" slide }}} {{{ Run the fibonacci.py in terminal and show the error output & switch back to slide }}} >>> python fibonacci.py

Now, let us run the fibonacci.py file. To do this, switch to the terminal & type "python fibonacci.py".

The tests fail as we just have a stub "fibonacci" function and no meaningful code in it. Our next step is to write just minimum code to pass our tests.
{{{ show "Fibonnaci" slide }}} {{{ switch to terminal }}} >>> python fibonacci.py

Modify the fibonacci stub function with given code & save the file. Now, switch to terminal and run it again as "python fibonacci.py".

{{{ pause }}} Observe that, there will be no errors, as the test passes successfully.
{{{ Show "Fibonacci - Recursive" slide }}} Finally, the same "fibonacci" function is modified to make it more readable and easy to understand using recursion. Pause this video here. Replace the "fibonacci" function with recursive one. Run the modified "fibonacci.py" file. The test should pass again without any errors. After successfully achieving this result, you can resume the video.
{{{ show "Summary" slide }}}

This brings us to the end of the tutorial. In this tutorial, we have learnt,

  1. The basic steps involved in Test driven development.
  2. How to use test cases.
  3. How to write simple tests for a function.
{{{ show "Evaluation" slide }}}

Here are some self assessment questions for you to solve,

  1. Design a TDD approach for a factorial function.
  2. Design a TDD approach for an armstrong function.

Try out the excercises for yourself & resume the video for solutions.
{{{ show "Factorial" slide}}} Given here is a TDD approach to a factorial function.
{{{ show "Armstrong" slide}}} Given here is a TDD approach to an armstrong function.
{{{ Show the SDES & FOSSEE slide }}}

Software Development techniques for Engineers and Scientists - SDES, is an initiative by FOSSEE. For more information, please visit the given link.

Free and Open-source Software for Science and Engineering Education - FOSSEE, is based at IIT Bombay which is funded by MHRD as part of National Mission on Education through ICT.
{{{ Show the ``About the Spoken Tutorial Project'' slide }}} Watch the video available at the following link. It summarises the Spoken Tutorial project.If you do not have good bandwidth, you can download and watch it.
{{{ Show the `` Spoken Tutorial Workshops'' slide }}}

The Spoken Tutorial Project Team conducts workshops using spoken tutorials, gives certificates to those who pass an online test.

For more details, contact contact@spoken-tutorial.org
{{{ Show the Acknowledgements slide }}} Spoken Tutorial Project is a part of the "Talk to a Teacher" project. It is supported by the National Mission on Education through ICT, MHRD, Government of India. More information on this mission is available at the given link.
{{{ Show the Thankyou slide }}} Hope you have enjoyed this tutorial and found it useful. Thank you!