TDD in Python Shuhsi Lin 2017/6/16 

Agenda More info on how to use this template at www.slidescarnival.com/help-use-presentation-template Testing ○ ○ ○ ○ Unit Test ○ ○ ○ ○ TDD ○ ○ 

Hello! 

Testing Software Testing 

Why Software Testing 1. Deliver the best application we can. 2. Lots of different devices, browsers, and operating systems 3. User really will do that – no matter how silly it seems. 4. One person to hundreds of people, even more, are using it. 5. To ensure that what we create does what it’s supposed to do. http://www.te52.com/testtalk/2014/08/07/5-reasons-we-need-software-testing/ Precision and Accuracy, Validation, Reliability, and Quality Delivery of high quality product or software application to customers 

Test Principles Principles are just for reference. I will not use them in practise. http://istqbexamcertification.com/what-are-the-principles-of-testing/ http://www.guru99.com/software-testing-seven-principles.html 

Testing methods and Types ○ ○ ○ 

Testing levels Unit testing Integration testing System testing Operational acceptance testing Developers White box Testers （ＱＡ, users) Black box 

“ Developers Ｓ 

Write test program to test 

Write test program to test 1. Instant Feedback ◦ ( Time (testing) << Time(debugging) ) 2. Regression Testing and Refactoring 3. API design 4. (Unit) test is Document 

Unit Test 

What Is Unit test? ● Smallest testable part of an application like functions, classes, procedures, interfaces. ● Breaking your program into pieces, and subjecting each piece to a series of tests ● should be done by the developers. http://istqbexamcertification.com/what-is-unit-testing/ Unit test is good, because ● Issues are found at early stage ● Unit testing helps in maintaining and changing the code ● Reducing the cost of bug fixes. ● Simplifying the debugging process 

Assert Telling the program to test that condition, and trigger an error if the condition is false. if not condition: raise AssertionError() >>> assert True >>> assert False Traceback (most recent call last) : File "", line 1, in AssertionError Assert = https://docs.python.org/3/reference/simple_stmts.html#assert 

class Calculator: def mod(self, dividend, divisor): remainder = dividend % divisor quotient = (dividend - remainder) / divisor return quotient, remainder if __name__ == '__main__': cal = Calculator() assert cal.mod(5, 3) == (1, 2) # 5 / 3 = 1 ... 2 assert cal.mod(8, 4) == (1, 0) # 8 / 4 = 2 ... 0 Assert example https://imsardine.wordpress.com/tech/unit-testing-in-python/ Traceback (most recent call last) : File "/Users/shuhsi/github/TDD-kata/test_calc.py ", line 11, in assert cal.mod(8, 4) == (1, 0) # 8 / 4 = 2 ... 0 AssertionError 

https://en.wikipedia.org/wiki/List_of_unit_testing_frameworks xUnit Framework ● Architecture for unit testing frameworks that are code-driven ● By Kent Beck ● Prescribes testing the fundamental units of software –examples: functions, methods, classes ● Distinguishes between failures and errors in a unit of software Each Test case has four-phase: ● Setup ● Exercise ● Verify (assertion) ● Teardown (cleanup) 

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Python Example https://docs.python.org/3/library/unittest.html import unittest class TestStringMethods (unittest.TestCase): def test_upper(self): self.assertEqual ('foo'.upper(), 'FOO') def test_isupper (self): self.assertTrue('FOO'.isupper()) self.assertFalse ('Foo'.isupper()) def test_split(self): s = 'hello world ' self.assertEqual (s.split(), ['hello', 'world']) # check that s.split fails when the separator is not a string with self.assertRaises (TypeError) : s. split(2) if __name__ == '__main__': unittest. main() 

import unittest class Calculator: def mod(self, dividend, divisor): remainder = dividend % divisor quotient = (dividend - remainder) / divisor return quotient, remainder class CalculatorTest (unittest.TestCase): def test_mod_with_remainder (self): cal = Calculator() self.assertEqual (cal.mod(5, 3), (1, 2)) def test_mod_without_remainder (self): cal = Calculator() self.assertEqual (cal.mod(8, 4), (1, 0)) def test_mod_divide_by_zero (self): cal = Calculator() assertRaises (ZeroDivisionError, cal.mod, 7, 1) if __name__ == '__main__': unittest. main() Subclass of unittest Prefix: test assertEqual Import unitest Run all test cases Raise error 

====================================================================== ERROR: test_mod_divide_by_zero (__main__.CalculatorTest) ---------------------------------------------------------------------- Traceback (most recent call last): File "/Users/shuhsi/github/TDD-kata/test_calc.py", line 22, in test_mod_divide_by_zero assertRaises(ZeroDivisionError, cal.mod, 7, 1) NameError: global name 'assertRaises' is not defined ====================================================================== FAIL: test_mod_without_remainder (__main__.CalculatorTest) ---------------------------------------------------------------------- Traceback (most recent call last): File "/Users/shuhsi/github/TDD-kata/test_calc.py", line 18, in test_mod_without_remainder self.assertEqual(cal.mod(8, 4), (1, 0)) AssertionError: Tuples differ: (2, 0) != (1, 0) First differing element 0: 2 1 - (2, 0) ? ^ + (1, 0) ? ^ ---------------------------------------------------------------------- Ran 3 tests in 0.009s FAILED (failures=1, errors=1) Show difference error 

TDD 

What Is TDD? ● Test-driven development ● A methodology of Implementing Software that relies on the repetition of a very short development cycle TDD is not ● a developing Tool ● a silver bullet for problems! ● the ONLY way to write good software! ○ But, if followed, will help you write solid software! 

TDD cycles http://blog.cleancoder.com/uncle-bob/2014/12/17/TheCyclesOfTDD.html 1. Create a unit tests that fails 2. Write production code that makes that test pass 3. Clean up the mess you just made 

Let’s Try it 

"Write a program that prints the numbers from 1 to 100. But for multiples of three print “Fizz” instead of the number and for the multiples of five print “Buzz”. For numbers which are multiples of both three and five print “FizzBuzz” FizzBuzz Problem http://codingdojo.org/kata/FizzBuzz/ Sample output 

import unittest class TestFizzBuzz(unittest.TestCase): def test_0_raise_value_error (self): with self.assertRaises(ValueError): FizzBuzz(0) Write a test (will fail) Not exist yet fizzbuzz_test.py 

import unittest from fizzbuzz import FizzBuzz class TestFizzBuzz(unittest.TestCase): def test_0_raise_value_error (self): with self.assertRaises(ValueError): FizzBuzz(0) Write a production code (will pass a test) class FizzBuzz(object): pass 

class FizzBuzz(object): pass Refactor class FizzBuzz(object): def __init__(self, number): raise ValueError() 

import unittest from fizzbuzz import FizzBuzz class TestFizzBuzz(unittest.TestCase): def test_0_raise_value_error (self): with self.assertRaises(ValueError): FizzBuzz(0) def test_1_does_mot -raise_value_error (self): assert FizzBuzz(1).number == 1 (iteration 2) Write a test (will fail) 

(iteration 2)Write a production code (will pass a test) class FizzBuzz(object): def __init__(self, number): if number == 0: raise ValueError() self.number =1 

https://youtu.be/JJk_HK2ZWGg 

What TDD can help you? https://www.madetech.com/blog/9-benefits-of-test-driven-development 1. Acceptance Criteria 2. Focus 3. Interfaces 4. Tidier Code 5. Dependencies 6. Safer Refactoring 7. Fewer Bugs 8. Increasing Returns 9. Living Documentation 

Testing/coding is so hard!! How to do it? https://www.youtube.com/watch?v=KijjEG_DQ34 

Code Kata and Dojo http://blog.agilepartner.net/code-kata-improve-your-coding-skills/ 

http://codingdojo.org/dojo/ http://www.skfscotland.co.uk/katas/kushanku_kata.gif 

More about testing and xDD ○ ○ ○ ○ ○ 

FURTHER READING: Uncle Bob Martin ◦ Clean code ◦ http://blog.8thlight.com/uncle-bob/archive.html Kent Beck ◦ Extreme Programming Explained ◦ Test Driven Development: By Example Is TDD Dead? Test-Driven Development with Python Essential TDD (Test-Driven Development) for Pythoners, Pycontw 2016 RSpec & TDD Tutorial by ihower 

Thanks!