The document discusses various unit testing frameworks and methodologies including JUnit, RSpec, and ScalaCheck, focusing on behavior testing, property testing, and mutation testing. It emphasizes the importance of clear and concise test descriptions while critiquing common practices in unit testing. The author also intertwines humor and personal anecdotes to engage the reader in the testing narrative.

1. The
hitchhicker’s
guide
to
unit
tes1ng
Rémy-­‐Christophe
Schermesser
@el_picador

2. Ruby!
Scala!
Java!
Python!
PHP!

3. Ruby!
Scala!
Java!
Python!
PHP!
But
don’t
forget
your
towel

4. Test::Unit
ScalaTest
jUnit
uniFest
PHPUnit

5. Test::Unit
ScalaTest
jUnit
uniFest
PHPUnit
Again
don’t
forget
your
towel

6. JUnit

7. assertEquals
At
the
beginning,
we
had

8. Then
assertThatMyTestFitsOn
OneLine(whatIExpect,
whatMyCodeIsDoing);

9. And
void
testWithCamelCase
ToReadItBeFer()
{
...
}

10. And
again
@Test
void
annotaZonsAreGood
ForYourHealth()
{
...
}

11. And
again
again
void
testMyTest()
{
Obj
obj
=
new
Obj();
//
10
lignes
of
things
assertEquals(…);
}

12. JUnit

13. JUnit
Mocks

14. JUnit
Fixtures
Mocks

15. JUnit
Behavior
tes1ng
with
RSpec

16. Problem
void
testMyTest()
{
Obj
obj
=
new
Obj();
//
10
lignes
of
things
assertEquals(…);
}

17. Behavior
tesZng,
don’t
test,
do
describe
Describe
what
your
program
should
do

18. One
test
One
(english)
sentence
Behavior
tesZng,
don’t
test,
do
describe

19. RSpec,
don’t
panic,
factorize
and
do
DSL

20. describe
CompaniesController
do
describe
"POST
create"
do
context
"when
recruiter
signed_in
with
no
company"
do
…
end
end
end

21. describe
CompaniesController
do
describe
"POST
create"
do
context
"when
recruiter
signed_in
with
no
company"
do
…
end
end
end

22. describe
CompaniesController
do
describe
"POST
create"
do
context
"when
recruiter
signed_in
with
no
company
an
email
is
sent"
do
…
end
end
end

23. let!(:recruiter)
{
login_recruiter
create(:recruiter,
company_id:
nil)
}
context
"when
good
params"
do
let(:params)
{
…
}
it
{
expect
{
post
:create,
params
}.to
change(Company,
:count).by
1
}
it
{
expect
{
post
:create,
params
}.to
change(Ac1onMailer::Base.deliveries,
:count).by
2
}
end
“When
recruiter
signed_in
with
no
company”

24. let!(:recruiter)
{
login_recruiter
create(:recruiter,
company_id:
nil)
}
context
"when
good
params"
do
let(:params)
{
…
}
it
{
expect
{
post
:create,
params
}.to
change(Company,
:count).by
1
}
it
{
expect
{
post
:create,
params
}.to
change(Ac1onMailer::Base.deliveries,
:count).by
2
}
end
“When
recruiter
signed_in
with
no
company”

25. let!(:recruiter)
{
login_recruiter
create(:recruiter,
company_id:
nil)
}
context
"when
good
params"
do
let(:params)
{
…
}
it
{
expect
{
post
:create,
params
}.to
change(Company,
:count).by
1
}
it
{
expect
{
post
:create,
params
}.to
change(Ac1onMailer::Base.deliveries,
:count).by
2
}
end
“When
recruiter
signed_in
with
no
company”

26. let!(:recruiter)
{
login_recruiter
create(:recruiter,
company_id:
nil)
}
context
"when
good
params"
do
let(:params)
{
…
}
it
{
expect
{
post
:create,
params
}.to
change(Company,
:count).by
1
}
it
{
expect
{
post
:create,
params
}.to
change(Ac1onMailer::Base.deliveries,
:count).by
2
}
end
“When
recruiter
signed_in
with
no
company”

27. Like
a
towel,
use
it
every
day

28. JUnit
Muta1on
tes1ng
Behavior
tes1ng
with
Javalanche

29. Code
coverage
has
limits
Code:
ctrl+c
Test:
ctrl+v

30. Code
a
class
and
test
it

31. Mutate
it

32. &&
++
!=
>
…
||
-­‐-­‐
==
<
…
Mutate
it

33. if(a
&&
b)
{
i++;
}
else
{
i-­‐-­‐;
}
if(a || b) {
i++;
} else {
i--;
}
if(a && b) {
i--;
} else {
i--;
}
Mutate
it

34. Kill
it

35. mvn
test
ant
-­‐f
javalanche.xml
mutaZonTest
Kill
it

36. Run
tests
Green
tests
Something’s
wrong

37. Run
tests
Red
tests
Great
job!

38. Coverage
data
Equivalent
mutant
if(index
>=
10)
break
and
if(index
==
10)
break
Selec1ve
muta1on
Parallel
execu1on
Choose
your
mutants
wisely
Using
code
coverage
to
reduce
the
tests
to
run
Speed-­‐up
The
right
tool

41. Behavior
tes1ng
JUnit
Property
tes1ng
Muta1on
tes1ng
with
ScalaCheck

42. How
to
test
string
concatenaZon
?
assert(
("ta"
+
"a")
==
"taa"
)

43. How
to
test
string
concatenaZon
?
assert(
("ta"
+
"a")
==
"taa"
)
assert(
("ta"
+
"b")
==
"tab"
)

44. How
to
test
string
concatenaZon
?
assert(
("ta"
+
"a")
==
"taa"
)
assert(
("ta"
+
"b")
==
"tab"
)
…

45. How
to
test
string
concatenaZon
?
assert(
("ta"
+
"a")
==
"taa"
)
assert(
("ta"
+
"b")
==
"tab"
)
assert(
("ta"
+
"z")
==
"taz"
)
…

46. How
to
test
string
concatenaZon
?
assert(
("ta"
+
"a")
==
"taa"
)
assert(
("ta"
+
"b")
==
"tab"
)
assert(
("ta"
+
"z")
==
"taz"
)
…
But
boring

47. ∀n∈N,
∃!k∈N
(n
=
2k
⋁
n
=
2k+1)
Remember
math
class?
∀n,
n
=
42

48. val
n:
Int
val
k:
Int
(n
==
2k
||
n
==
2k
+
1)
==
true
(n
%
2
==
0
||
n
%
2
==
1)
==
true
In
code

49. val
a:
String
val
b:
String
((a+b)
endsWith
b)
==
true
((a+b)
startsWith
a)
==
true
(a+b).length
==
a.length
+
b.length
String
concatenaZon
properZes

50. List[Int]
=>
isPalindrome(list)
(list.reverse
==
list)
==>
isPalindrome(list)
(list.reverse
!=
list)
==>
!isPalindrome(list)
Limits

52. Behavior
tesZng

Every
day
MutaZon
tesZng

CriZcal
code
Property
tesZng
à
CriZcal
code
Share
and
Enjoy

53. So
Long,
and
Thanks
for
All
the
Fish
Rémy-­‐Christophe
Schermesser
@el_picador

54. Rémy-­‐Christophe
Schermesser
@el_picador
Behavior
tesZng
Rspec
(ruby)
Jasmine
(javascript)
MutaZon
tesZng
Javalanche
(java)
Mutant
(ruby)
Property
tesZng
ScalaCheck
(scala)
QuickCheck
(haskell)
MrProper
(ruby)