1.
Got units?
Bengaluru, 20-22 November 2011

2.
TDD
Bengaluru, 20-22 November 2011

3.
RED
add a test, it won't pass
Bengaluru, 20-22 November 2011

4.
GREEN
implement the necessary code to make the test pass
Bengaluru, 20-22 November 2011

5.
REFACTOR
polish the code
Bengaluru, 20-22 November 2011

6.
TDD-ing Dijkstra's
shortest path algorithm
in PHP
Bengaluru, 20-22 November 2011

7.
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8.
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9.
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10.
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11.
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12.
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13.
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14.
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15.
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16.
github.com/odino/osidays
Bengaluru, 20-22 November 2011

17.
git checkout $step
Bengaluru, 20-22 November 2011

18.
Step 0/1
● create the directory structure
● add Symfony2 classloader as submodule
● init and update submodule
● (optional) create an empty class
Bengaluru, 20-22 November 2011

19.
Step 2
● write the test with the smallest
amount of code you think it's
necessary
Bengaluru, 20-22 November 2011

20.
Step 3
● add the Vertex class
● add the Graph class
● add an empty solve() method
for the algorithm class
Bengaluru, 20-22 November 2011

21.
Step 4
● implement the solve method
Bengaluru, 20-22 November 2011

22.
Step 5
● added all the methods
needed by the Dijkstra::solve()
● need to implement Graph::calculatePotentials()
Bengaluru, 20-22 November 2011

23.
Step 6
● a test is added for the Graph class
Bengaluru, 20-22 November 2011

24.
Step 7
● calculatePotentials() is tested
● half of our test-suite passes
● switch back to the Dijkstra's test
Bengaluru, 20-22 November 2011

25.
Step 8
● minor tweaks to make all the tests pass
Bengaluru, 20-22 November 2011

26.
Step 9
● potentials are assigned in the Graph class
but they should belong to the algorithm,
what about refactoring the code?
● since we move the only tested method of Graph
into Dijkstra's class, we can delete the GraphTest
Bengaluru, 20-22 November 2011

27.
Step 10
● since we like to be OO, we can connect
vertices through objects, and not
arrays anymore
Bengaluru, 20-22 November 2011

28.
Step 11
● we now need to fix the code which
uses vertices' connections as arrays
Bengaluru, 20-22 November 2011

29.
Step 12
● the library seems pretty complete
● PHPDoc is added
Bengaluru, 20-22 November 2011

30.
Step 13
● Oooops, we forgot to test a scenario:
in Dijkstra's algorithm we need vertices
connected by positive distance
● a test is added, verifying an exception
is raised through annotations
Bengaluru, 20-22 November 2011

31.
Step 14
● implementation
Bengaluru, 20-22 November 2011

32.
Step 15
● enter Mocking objects
Bengaluru, 20-22 November 2011

33.
Step 16
● Dijkstra::getGraph() seems to be useless
so we probably don't need any Graph class
Bengaluru, 20-22 November 2011

34.
Step 17
● removed Graph class
Bengaluru, 20-22 November 2011

35.
Step 18
● some tests rely on it, so we need to
eliminate old references to Graph
Bengaluru, 20-22 November 2011

36.
Step 19
● enter Data Providers
Bengaluru, 20-22 November 2011

37.
Step 20
● what about calculating the path between
not-connected vertices?
It should return null, so code is refactored
Bengaluru, 20-22 November 2011

38.
Step 21
● Dijkstra::solve() seems to do too
much things, so we split the method
● first demand potentials' calculation
● second demand path finding
● third demand raising the negative-potentials'
exception
● enter phploc
● enter code-coverage
Bengaluru, 20-22 November 2011

39.
Alessandro Nadalin
Bengaluru, 20-22 November 2011

40.
odino.org
Bengaluru, 20-22 November 2011

41.
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42.
@_odino_ #osidays
Bengaluru, 20-22 November 2011

43.
REST in peace: tomorrow, 12.45
Bengaluru, 20-22 November 2011

44.
Thank YOU!
@_odino_
Bengaluru, 20-22 November 2011