Thought Driven Development

Some thought on the way we Develop and Test our products

Transcript

1. THOUGHT DRIVEN DEVELOPMENT by @AlexeyBuzdin
2. @AlexeyBuzdin Developer / Trainer at
3. DOES THIS CODE WORK? def trySend (Mail mail) { try { mailService.send mail } catch (ServerTimeOutException e) { /* TODO: Handle error here */ } }
4. NO IDEA TO BE HONEST…
5. HOW TO MAKE SURE?
6. RUN THE THING!
7. ZE CODE AGAIN def trySend (Mail mail) { try { mailService.send mail } catch (ServerTimeOutException e) { /* TODO: Handle error here */ } }
8. ZE CODE AGAIN def trySend (Mail mail) { try { mailService.send mail } catch (ServerTimeOutException e) { /* TODO: Handle error here */ } } HOW MANY PATHS?
9. 3+ HOW MANY PATHS?
10. 3+ HOW MANY PATHS? HAPPY PATH SERVER TIMEOUT ?
11. 3+ HOW MANY PATHS? HAPPY PATH SERVER TIMEOUT ?
12. 3+ HOW MANY PATHS? HAPPY PATH SERVER TIMEOUT ?
13. ZE CODE AGAIN def trySend (Mail mail) { try { mailService.send mail } catch (ServerTimeOutException e) { /* TODO: Handle error here */ } }
14. 3+ HOW MANY PATHS? HAPPY PATH SERVER TIMEOUT NULL POINTER
15. RUN THE THING 1!
16. RUN THE THING 1! RUN THE THING 2!
17. RUN THE THING 1! RUN THE THING 2! RUN THE THING 3!
19. WHO HAS DONE THIS?
20. DEBUGGING CODE TO UNDERSTAND WHERE IS THE FAILURE
21. IN 99% THIS IS WRONG!
22. TESTS
23. TESTS ARE MADE TO MAKE YOU FEEL SECURE!
24. LIKE A LOVELY HUG ♥
25. YOU NEED TO ADD SOMETHING TO THIS CODE
26. public byte[] scaleImage(InputStream is, int maxWidth, int maxHeight, ImageType type) throws IOException { if (is == null) throw new IOException(String.format("Input stream is unavailable for image type %s", type.getMime())); BufferedImage source = ImageIO.read(is); int width = source.getWidth(); int height = source.getHeight(); int scaledWidth = width; int scaledHeight = height; if (width > maxWidth) { scaledWidth = maxWidth; scaledHeight = (int) Math.ceil((scaledWidth * height * 1.0) / width); } if (scaledHeight > maxHeight) { scaledHeight = maxHeight; scaledWidth = (int) Math.ceil((scaledHeight * width * 1.0) / height); } source = (width < maxWidth || height < maxHeight) ? subImage(source, width, height, maxWidth, maxHeight) : scale(source, width, height, scaledWidth, scaledHeight); ByteArrayOutputStream stream = new ByteArrayOutputStream(); ImageIO.write(source, type.getMime(), stream); return stream.toByteArray(); }
27. NO TESTS…
28. NO TESTS… DO YOU FEEL SECURE?
29. TESTS ARE AWESOME!
30. THUS…
31. LETS SELL THEM!
32. LETS SELL THEM! EVANGELIZE
33. (TDD) TEST-DRIVEN DEVELOPMENT
34. CLASSIC TDD 1. ADD A TEST 2. RUN ALL TESTS 3. WRITE SOME CODE 4. RUN TESTS 5. REFACTOR CODE 6. REPEAT
35. CONFIDENCE MEANS STRICT RULES?
36. I WANT TO BE A BADASS!
37. AWESOME AND CONFIDENT
39. EATING ELEPHANT PIECE BY PIECE
40. EATING ELEPHANT PIECE BY PIECE AND KEEPING HIM ALIVE IN THE PROCESS!
41. ATOMIC COMMITS?
42. SINGLE COMMIT OR SINGLE TEST DOES NOT BRING ANY VALUE
43. SINGLE TEST DOES NOT BRING ANY VALUE MERGE WITH MASTER DOES SINGLE COMMIT OR
44. SINGLE TEST DOES NOT BRING ANY VALUE TESTED USER STORY DOES SINGLE COMMIT OR
45. SO WHY EXTRA EFFORT?
46. SO WHY EXTRA EFFORT? BECAUSE IT’S COOL!
47. Test-Driven Development
48. Kent Beck stated that TDD: - encourages simple designs - inspires confidence Test-Driven Development
49. TOOLS ARE MEANT TO HELP
50. Kent Beck stated that TDD: - encourages simple designs - inspires confidence TDD acts as a self-documenting code Test-Driven Development
51. Kent Beck stated that TDD: - encourages simple designs - inspires confidence TDD acts as a self-documenting code Test-Driven Development but on which level?
52. Kent Beck stated that TDD: - encourages simple designs - inspires confidence TDD acts as a self-documenting code Test-Driven Development but on which level? LETS THINK!
53. THOUGHT DRIVEN DEVELOPMENT
54. AS A USER I WANT TO POST A TWEET
55. ARE YOU CONFIDENT ABOUT THIS?
56. NO? THEN TEST IT!
57. BUT WHAT IF CONNECTION FAILS?
58. UNSURE? THEN TEST IT!
59. FEATURES ARE NOT LIKELY TO BE REMOVED
60. FEATURES ARE LIKELY TO EVOLVE
61. FEATURES ARE LIKELY TO EXPAND
62. def join(List<String> tokens, String separator) HOW MANY TEST WOULD YOU WRITE?
63. def join(List<String> tokens, String separator) {
 def sb = new StringBuilder()
 boolean first = true
 for (String item : tokens)
 {
 if (first) first = false
 else sb.append separator
 sb.append item
 }
 return sb.toString
 } HOW MANY TEST WOULD YOU WRITE?
64. def join(List<String> tokens, String separator) {
 def sb = new StringBuilder()
 boolean first = true
 for (String item : tokens)
 {
 if (first) first = false
 else sb.append separator
 sb.append item
 }
 return sb.toString
 } HOW MANY TEST WOULD MAKE YOU CONFIDENT?
65. @Test def joinsStrings() { def actual = util.join(Arrays.asList("hello", "world"), ";") assertThat(actual, equalTo "hello;world") } IS ONE ENOUGH?
66. TECHNICAL BOILERPLATE WILL LIKELY TO BE CHANGED
67. TECHNICAL BOILERPLATE AND IT’S TESTS WILL LIKELY TO DIE
68. GOOD TEST IS LIKELY TO BE #BROKEN
69. TEST BEHAVIOR, NOT CODE!
70. BUT TEST AS LOW AS IT MAKES SENSE
71. IDENTIFY INDEPENDENT MODULES/LAYERS
72. MAKE END-TO-END TESTS FOR CORE FUNCTIONALITY
73. ALWAYS TEST PUBLIC API EXTENSIVELY!
74. SOMETIMES LET CLIENTS TEST YOUR APP!
75. Scenario: New Customer is retrieved by ID Given request body from file json/newCustomer.json When the client performs POST request on /customers Then status code is 201 And header Location end with customers/(.+) And assign variable "{(location)}" to header "Location" value When the client performs GET request on {(location)} Then status code is 200 And response body contains properties from file json/newCustomer.json Acceptance Test-Driven Development (ATDD)
76. ALWAYS TEST POINTS OF INTEGRATIONS FOR TRICKY CASES!
77. ALWAYS TEST INPUT
78. ALWAYS EXTENSIVELY TEST CODE, THAT MAKES YOU MONEY!
79. CODE COVERAGE
80. CODE COVERAGE IS YOUR SIDEKICK
81. CODE COVERAGE IS YOUR SIDEKICK NOT A COMPETITOR
82. TAKE AWAYS
83. TAKE AWAYS LET TESTS GUIDE YOUR HAND
84. TAKE AWAYS LET TESTS GUIDE YOUR HAND TEST FOR EACH FAILURE ACCOUTERED
85. TAKE AWAYS LET TESTS GUIDE YOUR HAND TEST FOR EACH FAILURE ACCOUTERED TEST MEANINGFUL CODE
86. TAKE AWAYS LET TESTS GUIDE YOUR HAND TEST FOR EACH FAILURE ACCOUTERED TEST MEANINGFUL CODE TEST-DOCUMENT PUBLIC API
87. BUT SOMETIMES HEAR OUT YOUR GUTS!
88. Q&A @AlexeyBuzdin #bycraft