The why and how the original specs project was rewritten to become specs2

1. Go functional!

3. tour
import IncredibleStringReverser._
class ReverserSpec extends Specification {
"a reversed empty string must be empty" in {
reverse("") must_== ""
}
"a reversed empty string must really *be empty*" in {
reverse("") must be empty
}
"a reversed string must be reversed abc -> cba" in {
reverse("abc") must be_==("cba")
}
"a longer string must also be reversed. Whoops!" in {
reverse("abcdef") must be_==("xxxxx")
}
}

4. tour
"a reversed empty string must be empty" in {
reverse("") must be empty
}

5. tour

6. tour

7. Sham
e

8. Mutability

9. Concurrency

10. Acceptance

11. Wh
y
The idea
User
Design
Program

12. Go Functional!

13. Referential
transparency

Immutability

14. behavior
pipelined
F
Pemergent
behavior
Processing data
structures
OO

15. Wh
y
The idea
User
Design
Program

16. Starting point
instructions != expressions

17. Nesting
Precedence:
+
!
^

18. Formatting
Text
Example
Text
Example
Example

19. Formatting
p
br
end
t, t(i)
bt, bt(i)
acceptance

20. Context

21. doBefore
withDb.apply(e2)

22. Wh
y
The idea
User
Design
Program

23. Run
execute
levels
select
sequence
arguments
statistics
to text
to html

24. Laziness vs evaluation

25. Iterating

26. Traverse
A data
structure to
traverse
the
accumulation
the
mapping

27. Applicative magic?
Lots of instances:
• State
• List
• Monad
• Monoid
simple
composable Type inference
is hard,
Let’s go shopping!

28. Reducer
aggregation
“parallel” composition
mapping
specs2 reducers:
• Levels
• Statistics
• Arguments
• Text
• Html

29. Wh
y
The idea
User
Design
Program

30. Trees
Text
Example 1 Example 2
Suite
Description
Test
Description 1
Test
Description 2
Suite
Description
fChildren = TD1, TD2

31. TreeLoc

32. TreeLoc
Anti-XML
The non-violent solution

33. Concurrency
a concurrent
task
=> Promise[Seq[ExecutedFragment]]

34. Exceptions

35. Exceptions

36. Exceptions

37. Mocks

38. Mutability
Nothing here!
Throws
exception

39. Configuration
Part of the flow
named parameters + defaults
nested ‘record’

40. Configuration
Implicits
implicit
arguments
default
value

41. Watch out!
recursivity
val (a,b) = c
val in traits
lost expressions

42. Conclusion
• Reliability
• Concurrency
• Composition
• Less mocks
• val/vars
• DSL
• Type inference
• Learning curve
• Gotchas