Test Driven Development SN Biggs York Plasma Institute TDD | 7th - - PowerPoint PPT Presentation

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Test Driven Development SN Biggs York Plasma Institute TDD | 7th - - PowerPoint PPT Presentation

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Test Driven Development SN Biggs York Plasma Institute TDD | 7th July 2017 | 1/40 Introduction Image ref: https://usercontent2.hubstatic.com/8530569 f520.jpg TDD | 7th July 2017 | 2/40 Outline Unit Testing Unit Testing is a Safety Net Unit

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SLIDE 1

Test Driven Development

SN Biggs

York Plasma Institute TDD|7th July 2017|1/40

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SLIDE 2

Introduction

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SLIDE 3

Outline

Unit Testing

Unit Testing is a Safety Net Unit Test Structure: Setup, Exercise, Assert xUnit – The Testing Framework Exercise – Write Some Unit Tests

Test Driven Development (TDD)

A Different Mindset Test First!? Fail, Pass, Refactor: A Simple Example Exercise – Take TDD for a Test Drive

A Word of Warning: Pick the Right Tool for the Right Job Summary and Further Reading

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SLIDE 4

Unit Testing is a Safety Net

Image ref: http://www.fitnessbin.com/wp-content/uploads/2015/12/Rock-Climbing-4.jpg TDD|7th July 2017|4/40

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SLIDE 5

Unit Testing is a Safety Net

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SLIDE 6

Unit Testing is a Safety Net

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SLIDE 7

Unit Testing is a Safety Net

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SLIDE 8

Unit Testing is a Safety Net

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SLIDE 9

Unit Testing is a Safety Net

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SLIDE 10

Unit Testing is a Safety Net

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SLIDE 11

Unit Testing is a Safety Net

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SLIDE 12

Unit Testing is a Safety Net

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SLIDE 13

Unit Testing is a Safety Net

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SLIDE 14

Test Structure: Setup, Exercise, Assert

class Calculator(): def add(self, augend, addend): 'Adds the addend to the augend' return augend + addend

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SLIDE 15

Test Structure: Setup, Exercise, Assert

def testAddBothPositive(self): # Setup a = 3 b = 2 calc = Calculator() # Specify expected result expected = 5 # Exercise system under test actual = calc.add(a, b) # Verify result self.assertEqual(actual, expected)

TDD|7th July 2017|8/40

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SLIDE 16

xUnit - The Testing Framework

Began as sUnit for the Smalltalk language by Kent Beck in 1998 Since ported to many languages (cUnit, cppUnit, fUnit, pyUnit, etc.) Object-oriented - test classes inherit assertions Provides test suites, test runners, formatted test results, etc.

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SLIDE 17

xUnit - The Testing Framework

import unittest from Calculator import Calculator class testCalculator(unittest.TestCase): def setUp(self): self.calc = Calculator() def testAddBothPositive(self): 'Tests that two positive numbers are added correctly' # Exercise system under test and verify result self.assertEqual(self.calc.add(3, 2), 5)

TDD|7th July 2017|10/40

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SLIDE 18

xUnit - The Testing Framework

To run the unit tests (from bash): $ python -m unittest module[.class[.test]] [-v] e.g. $ python -m unittest testCalculator.testCalculator.testAddBothPositive

  • r discover tests automatically:

$ python -m unittest discover

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SLIDE 19

Exercise - Write Some Unit Tests

1 Download my basic calculator class∗ from here: http://www-

users.york.ac.uk/∼snb519/coding-club-tdd-examples/Calculator.py

2 Write a test class, testCalculator.py, that extends unittest.TestCase (see

slide 10)

3 Write tests (see slide 8) for adding different combinations of numbers, e.g.

both positive, both negative, one of each, floats, etc.

4 Run the tests (see slide 11) to see what the test results look like – try with

and without the -v flag, and try running individual tests and test discovery

5 Try changing Calculator.py to see what failing tests look like 6 Extension - can you write any tests that should pass but actually fail, e.g.

test that passing in strings is handled correctly

∗You can also get the slides here:

http://www-users.york.ac.uk/∼snb519/coding-club-tdd-examples/slides.pdf

TDD|7th July 2017|12/40

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SLIDE 20

A Different Mindset

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SLIDE 21

Test First!?

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SLIDE 22

Test First!?

1 Identify desired functionality 2 Write failing test 3 Make it compile as quickly as possible 4 Make it pass a quickly as possible 5 Remove duplication while maintaining 100% pass rate 6 Repeat as required

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SLIDE 23

Test First!?

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SLIDE 24

Fail, Pass, Refactor: A Simple Example

1 Identify desired functionality 2 Write failing test 3 Make it compile as quickly as possible 4 Make it pass a quickly as possible 5 Remove duplication while maintaining 100% pass rate 6 Repeat as required

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SLIDE 25

Fail, Pass, Refactor: A Simple Example

1 Identify desired functionality 2 Write failing test 3 Make it compile as quickly as possible 4 Make it pass a quickly as possible 5 Remove duplication while maintaining 100% pass rate 6 Repeat as required

TDD|7th July 2017|18/40

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SLIDE 26

Fail, Pass, Refactor: A Simple Example

def testSubtractBothPositive(self): 'Tests that two positive numbers are subtracted correctly' # Exercise system under test and verify result self.assertEqual(self.calc.subtract(3, 2), 1)

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SLIDE 27

Fail, Pass, Refactor: A Simple Example

E =============================================================== ERROR: testSubtractBothPositive (testCalculator.testCalculator) Tests that two positive numbers are subtracted correctly

  • Traceback (most recent call last):

File "testCalculator.py", line 40, in testSubtractBothPositiv self.assertEqual(self.calc.subtract(3, 2), 1) AttributeError: Calculator instance has no attribute 'subtract'

  • Ran 1 test in 0.000s

FAILED (errors=1)

TDD|7th July 2017|20/40

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SLIDE 28

Fail, Pass, Refactor: A Simple Example

1 Identify desired functionality 2 Write failing test 3 Make it compile as quickly as possible 4 Make it pass a quickly as possible 5 Remove duplication while maintaining 100% pass rate 6 Repeat as required

TDD|7th July 2017|21/40

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SLIDE 29

Fail, Pass, Refactor: A Simple Example

def subtract(self): pass

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SLIDE 30

Fail, Pass, Refactor: A Simple Example

E =============================================================== ERROR: testSubtractBothPositive (testCalculator.testCalculator) Tests that two positive numbers are subtracted correctly

  • Traceback (most recent call last):

File "testCalculator.py", line 40, in testSubtractBothPositiv self.assertEqual(self.calc.subtract(3, 2), 1) TypeError: subtract() takes exactly 1 argument (3 given)

  • Ran 1 test in 0.000s

FAILED (errors=1)

TDD|7th July 2017|23/40

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SLIDE 31

Fail, Pass, Refactor: A Simple Example

def subtract(self, minuend, subtrahend): pass

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SLIDE 32

Fail, Pass, Refactor: A Simple Example

F =============================================================== FAIL: testSubtractBothPositive (testCalculator.testCalculator) Tests that two positive numbers are subtracted correctly

  • Traceback (most recent call last):

File "testCalculator.py", line 40, in testSubtractBothPositiv self.assertEqual(self.calc.subtract(3, 2), 1) AssertionError: None != 1

  • Ran 1 test in 0.000s

FAILED (failures=1)

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SLIDE 33

Fail, Pass, Refactor: A Simple Example

1 Identify desired functionality 2 Write failing test 3 Make it compile as quickly as possible 4 Make it pass a quickly as possible 5 Remove duplication while maintaining 100% pass rate 6 Repeat as required

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SLIDE 34

Fail, Pass, Refactor: A Simple Example

def subtract(self, minuend, subtrahend): return 1

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SLIDE 35

Fail, Pass, Refactor: A Simple Example

.

  • Ran 1 test in 0.000s

OK

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SLIDE 36

Fail, Pass, Refactor: A Simple Example

1 Identify desired functionality 2 Write failing test 3 Make it compile as quickly as possible 4 Make it pass a quickly as possible 5 Remove duplication while maintaining 100% pass rate 6 Repeat as required

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SLIDE 37

Fail, Pass, Refactor: A Simple Example

def subtract(self, minuend, subtrahend): return 3 - 2

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SLIDE 38

Fail, Pass, Refactor: A Simple Example

.

  • Ran 1 test in 0.000s

OK

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SLIDE 39

Fail, Pass, Refactor: A Simple Example

def subtract(self, minuend, subtrahend): return minuend - 2

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SLIDE 40

Fail, Pass, Refactor: A Simple Example

.

  • Ran 1 test in 0.000s

OK

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SLIDE 41

Fail, Pass, Refactor: A Simple Example

def subtract(self, minuend, subtrahend): return minuend - subtrahend

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SLIDE 42

Fail, Pass, Refactor: A Simple Example

.

  • Ran 1 test in 0.000s

OK

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SLIDE 43

Fail, Pass, Refactor: A Simple Example

1 Identify desired functionality 2 Write failing test 3 Make it compile as quickly as possible 4 Make it pass a quickly as possible 5 Remove duplication while maintaining 100% pass rate 6 Repeat as required

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SLIDE 44

Exercise - Write Some Unit Tests

1 Using Calculator.py and testCalculator.py that you have already developed,

test and implement calc.multiply(multiplicand, multiplier) and calc.divide(divend, divisor) using TDD

2 Implement some extra features using TDD, e.g.

handling two numbers passed in as strings element-wise array operations (see numpy.testing.assert array equals) raising exceptions for invalid inputs (see unittest.TestCase.assertRaises) printing to screen when an optional argument is given (redirect sys.stdout) calculations on a custom class yet to be defined (pass in a mock subclass)

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SLIDE 45

A Word of Warning

Pick the right tool for the right job!

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SLIDE 46

Summary

Unit Testing

Unit Testing is a Safety Net Unit Test Structure: Setup, Exercise, Assert xUnit is The Testing Framework

Test Driven Development (TDD)

A Different Mindset Test First! Fail, Pass, Refactor

Pick the Right Tool for the Right Job

TDD|7th July 2017|39/40

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SLIDE 47

Further Reading

Beck, K 2003 “Test-driven Development: By Example” Addison-Wesley, Kent Beck signature book. Feathers, M 2004 “Working Effectively with Legacy Code” Pearson Education, Robert C. Martin Series. Martin, RC 2008 “Clean Code: A Handbook of Agile Software Craftsmanship” Pearson Education. Hunt, A and Thomas, D 1999 “The Pragmatic Programmer: From Journeyman to Master” Pearson Education.

Image ref: http://d.gr-assets.com/books/1372039943l/387190.jpg TDD|7th July 2017|40/40