Identify and Exploit Behavioral Boundaries for Unit Testing

BW12
Session
6/8/16 4:15 PM

Identify and Exploit Behavioral
Boundaries for Unit Testing

Presented by:

Rob Myers
Agile Institute

Brought to you by:

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Rob Myers
Agile Institute

The founder of Agile Institute, Rob Myers teaches courses that are always a blend
of fun and practical hands-on labs, “Training From the Back of the Room” learning
techniques, and relevant first-person stories from both successful and not-so-
successful agile implementations. With thirty years of professional experience
with software development teams, Rob has been training and coaching
organizations in Scrum and Extreme Programming since 1998. He currently works
with tiny start-ups and huge Fortune 100 multinationals, helping them with
cultural change and essential practices from Scrum, kanban, XP, and lean.

6/5/16
1
5 June 2016 © Agile Institute 2008-2016 1
Identify & Exploit
Behavioral
Boundaries
for
Unit Testing
Rob Myers
@agilecoach
Better Software West
08 June 2016
Café!
Unit Test
A test of one smallest bit of
behavior.
Also known these days as a
microtest.

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“As the tests get more specific,
the code gets more generic.”
– Bob Martin

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“The more code you write
without testing the behavioral
boundaries, the harder they are
to find & test later.”
– me
triangulation

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dial setting
percentmanufacturermaximum

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Pretend java.util.Set is BROKEN!
We need our own Set class with the
capabilities of creating unions & intersections;
checking if a set is empty; and also if it is equal
to, a superset of, or a subset of another set.
empty?

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@Test
public void isEmptyWhenConstructed() {
Set set = new Set();
assertThat(set.isEmpty(), is( true ));
}
not empty
3

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@Test
public void isNotEmptyWhenItemAdded() {
set.addElement( 3 );
assertThat(set.isEmpty(), is( false ));
}

@Test
public void isEmptyWhenConstructed() {
assertThat(set.isEmpty(), is( true ));
}
@Test(expected=IllegalArgumentException.class)
public void shouldNotAcceptNegativeNumbers() {
set.addElement( -1 );
}
-1

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A
B
1 2
3
5
84
6
7
9

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boolean subsetOf(Set other)
{
return size() <= other.size();
}

boolean supersetOf(Set other)
{
return size() >= other.size();
}

A
B
1 2
3
5
84
6
7
9
C
10
11
12

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Hungover Intern Principle
We write the microtests that will
warn a hung-over intern six months
from now as to why the
implementation is the way it is—
however simple or complex, efficient
or slow it may be.
*Protects against mistakes, not sabotage.
*
In order to be an acceptable password, a string
must:
q Have a length greater than 7 characters.
q Contain at least one alphabetic character.
q Contain at least one digit.
q Contain a special character.
q First character must be special or digit.
Password Strength Checker

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12345678
Good Bad
1234567
1234567B 12345678
Rule
Length > 7
Has alpha
passw0rd passwordHas digit
passw0rd? passw0rdHas special
?passw0rd passw0rd?1st special/
digit 4password?
?passw0rd
Good Bad
?passw0
?passw0rd ?1234567
Rule
Length > 7
Has alpha
?passw0rd ?passwordHas digit
?passw0rd passw0rdHas special
?passw0rd passw0rd?1st special/
digit 4password?

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combinations
X Y Z
A C E
A D E
A C F
A D F
B C E
B D E
B C F
B D F
pair-wise testing
X Y Z
A C E
A D E
A C F
A D F
B C E
B D E
B C F
B D F
X Y Z
A C E
A D F
B D E
B C F

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Listen to the Microtests
If you have difficulty unit-testing
something,
this is indicating an opportunity to
improve the design.
Rule
+ bool passes(string pw)
PasswordStrengthChecker
+ bool isStrong(
string password)
LengthGT7 HasDigitHasAlpha
HasSpecial FirstSpecialOrDigit

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12345678
Good Bad
1234567
A3, 3A, 3A3 3
Rule
Length > 7
Has alpha
3A, A3, A3A AHas digit
AB$, A$B AHas special
$A, 3A A$, A31st special/
digit
Rule
+ bool isStrong(
string password)
LengthGT7 HasDigitHasAlpha
HasSpecial FirstSpecialOrDigit

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Rule
+ bool isStrong(
string password)
MockRule
+ void setPassesTo(bool p)
+ bool passesWasCalled()
LengthGT7 HasAlpha
HasSpecial
ExamplesBoundary type
True / False
Valid / Invalid
Happy / Unhappy
Conditional
Iterative
Comparative Greater Than
Less Than
Before / After
Zero / One / Many
Subtype
*
* Examples! Not intended as a comprehensive list.

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Rob.Myers@agileInstitute.com
https://www.linkedin.com/in/robmyers64
@agilecoach

Identify and Exploit Behavioral Boundaries for Unit Testing

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