TDD in Python

Transcript

1. TDD in Python
   Shuhsi Lin
   2017/6/16
   

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2. Agenda
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   Testing
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   Unit Test
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   TDD
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3. Hello!
   

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4. Testing
   Software Testing
   

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5. 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
   

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6. 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
   

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7. Testing methods and Types
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8. Testing levels
   Unit testing
   Integration testing
   System testing
   Operational acceptance
   testing
   Developers
   White box
   Testers （ＱＡ, users)
   Black box
   

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9. “
   Developers
   Ｓ
   

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10. Write test program to test
    

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11. 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
    

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12. Unit Test
    

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13. 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
    

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14. 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
    

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15. 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
    

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16. 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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18. 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()
    

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19. 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
    

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20. ======================================================================
    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
    

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21. TDD
    

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22. 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!
    

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23. 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
    

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24. Let’s Try it
    

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25. "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
    

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26. 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
    

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27. 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
    

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

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29. 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)
    

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30. (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
    

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31. https://youtu.be/JJk_HK2ZWGg
    

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32. 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
    

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

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

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

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36. More about
    testing and xDD
    ○
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37. 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
    

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38. Thanks!
    

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