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Getting Existing Code Under Tests

@LlewellynFalco

90% Coverage in 1 Hour

1. Lock simple code2. Lock complex code3. Lock system configuration

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POP QUIZ

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QUESTION 1

public void closeConnection(){

var con = getConnectionForThread();if (con == null){

try{

con.close();}catch{

//ignore}

}}

What’s Wrong With this code?

Close Connection

doesn’t

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POSSIBLE FIXES:

1) CHANGE CODE

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POSSIBLE FIXES:

1) CHANGE CODE2) CHANGE NAME

OnlyPretendToCloseConnection()

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2 WRONGS != RIGHT

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But 3 Lefts Do!

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QUESTION 2

public double calculate(double amount)

{

int step1 = (int) (amount * 2);

double step2 = step1 * 1.5;

return step2;

}

Original Code

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?

1 => 3

ORIGINALREFACTORED

1 => 3

-1 => -3

4 => 12

3.2 => 9.6

-1 => -3

4 => 12

3.2 => 9

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WHY?

public double calculate(double amount)

{

int step1 = (int) (amount * 2);

double step2 = step1 * 1.5;

return step2;

}

Original Code

RoundsDown

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HOWIMPORTANT IS

0.6?

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FONT SIZE?

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BANKING?

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MEDICATION?

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QUESTION 3

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THESE 415 LINES HAVE BEEN REFACTORED TO THESE 213 LINES.

IS THERE A BUG?

ORIGINAL

REFACTORED

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ANSWER:

ARE THE TESTS STILLPASSING?

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HOW?

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Benefits of Unit Tests

1) Specification

2) Feedback

3) Regression

4) Granularity

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Benefits of Unit Tests

1) Specification

2) Feedback

3) Regression

4) Granularity

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Regression

If I used to get :

Then I still get :

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LOCKINGTEST

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FUNCTIONALIS EASY

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WHAT DOES THAT MEAN?

Functional(referential transparency)

Deterministic

All inputs in

All results out

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public double calculate(double amount){

int step1 = (int) (amount * 2);double step2 = step1 * 1.5;return step2;

}

All results out

All inputs in

Deterministic

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CAN I RUN THE CODE?

DOES IT ALWAYS PRODUCETHE SAME THING?

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public int Advance(){

return steps++;}

All inputs in?

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public int age(DateTime birthDate){

var timeSpan = DateTime.Now -birthDate;

var age = DateTime.MinValue +timeSpan;

return age.Year-1;}

All inputs in?

Deterministic?

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public void saveFile(Person info, string fileName){

File.WriteAllText(fileName, info.ToString());}

All results out?

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DEMO:

LOCKING FUNCTIONAL

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POKE

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LOCKINGNON-FUNCTIONAL

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NON-FUNCTIONALIS HARD

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Reduce To Functional

Easy

Hard

Yes

No

Functional

?

Reduce to

Functional

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LoggingLog

Easy

Capture of

behavior

Hard

public Logs LegacyCode(Inputs[] i)

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Files(name & size is usually enough)

FileA 34,368FileB 15,632FileC 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

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pluralsight.com/kids

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Contact Information

@LlewellynFalco

http://LlewellynFalco.Blogspot.com

http://www.approvaltests.com

http://lfal.co/ExtraResources