This document discusses getting existing code under tests and the benefits of unit testing. It provides examples of code and questions to test understanding of unit testing and functional vs non-functional testing. Functional tests are described as easier since they isolate code and ensure consistent outputs for given inputs, while non-functional tests involving things like concurrency are more difficult to test.

2. Getting Existing Code Under Tests
@LlewellynFalco
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3. 90% Coverage
in 1 Hour

4. 1. Lock simple code
2. Lock complex code
3. Lock system configuration

5. POP QUIZ
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6. QUESTION 1
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7. public void closeConnection()
{
var con = getConnectionForThread();
if (con == null)
{
try
{
con.close();
}
catch
{
//ignore
}
}
}
What’s Wrong With this code?
Close
Connection
doesn’t

8. POSSIBLE FIXES:
1) CHANGE CODE
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9. POSSIBLE FIXES:
1) CHANGE CODE
2) CHANGE NAME
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10. OnlyPretendToCloseConnection()

11. 2 WRONGS != RIGHT
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But 3 Lefts
Do!

13. QUESTION 2
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14. public double calculate(double amount)
{
int step1 = (int) (amount * 2);
double step2 = step1 * 1.5;
return step2;
}
Original Code

15. public double calculate(double
amount)
{
int step1 = (int) (amount * 2);
double step2 = step1 * 1.5;
return step2;
}
public double calculate(double
amount)
{
return amount * 3;
}
Is this ok?

16. REFACTORED ORIGINAL
1 => 3
1 => 3
-1 => -3
4 => 12
3.2 => 9.6
-1 => -3
4 => 12
3.2 => 9

17. WHY?
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18. public double calculate(double amount)
{
int step1 = (int) (amount * 2);
double step2 = step1 * 1.5;
return step2;
}
Original Code
Rounds
Down

19. HOW
IMPORTANT IS
0.6?
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20. FONT SIZE?
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21. BANKING?
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22. MEDICATION?
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24. QUESTION 3
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25. THESE 415 LINES HAVE BEEN
REFACTORED TO THESE 213 LINES.
IS THERE A BUG?
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26. REFACTORED
ORIGINAL 

27. ANSWER:
ARE THE
TESTS STILL
PASSING?
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30. HOW?
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31. Benefits of Unit Tests
1) Specification
2) Feedback
3) Regression
4) Granularity
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32. Benefits of Unit Tests
1) Specification
2) Feedback
3) Regression
4) Granularity
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33. Regression
If I used to get :
Then I still get :
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34. LOCKING
TEST
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35. FUNCTIONAL
IS EASY
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36. WHAT DOES
THAT MEAN?
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37. Functional
(referential transparency)
Deterministic
All inputs in
All results out

38. All inputs in
public double calculate(double amount)
{
int step1 = (int) (amount * 2);
double step2 = step1 * 1.5;
return step2;
}
All results out
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Deterministic

39. CAN I RUN THE CODE?
DOES IT ALWAYS PRODUCE
THE SAME THING?
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40. public int Advance()
{
return steps++;
}
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redistributed without the express consent of Mitchell International. ©2014 Mitchell International, Inc.
All inputs in?

41. public int age(DateTime birthDate)
{
var timeSpan = DateTime.Now -
birthDate;
var age = DateTime.MinValue +
timeSpan;
return age.Year-1;
}
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All inputs in?
Deterministic?

42. All results out?
public void saveFile(Person info, string fileName)
{
File.WriteAllText(fileName, info.ToString());
}
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DEMO:
LOCKING
FUNCTIONAL

44. POKE
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45. LOCKING
NON-FUNCTIONAL
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46. NON-FUNCTIONAL
IS HARD
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47. Functional
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Reduce To
Functional
Easy
Hard
Yes
No
?
Reduce to
Functional

48. Log
Logging Easy
Capture of
behavior
Hard
public Logs LegacyCode(Inputs[] i)
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Files
(name & size is usually enough)
FileA 34,368
FileB 15,632
FileC 28,453
public FileListing LegacyCode(Inputs[] i)

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Databases
✔
public SqlStatements LegacyCode(Inputs[] i)

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System
& Runtime
Configuration
Start
Log
Easy Capture
of
Configuration
public RuntimeConfig LegacyCode(Inputs[] i)

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www.ApprovalTests.com
21 episode YouTube series

53. pluralsight.com/kids
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Contact Information
@LlewellynFalco
http://LlewellynFalco.Blogspot.com
http://www.approvaltests.com
http://lfal.co/ExtraResources