Got units? @ Osidays 2011 India 11-20-2011

Got units?Bengaluru, 20-22 November 2011

Bengaluru, 20-22 November 2011

TDD


REDadd a test, it won't pass


GREENimplement the necessary code to make the test pass


REFACTORpolish the code


TDD-ing Dijkstra'sshortest path algorithm

in PHP











github.com/odino/osidays


git checkout $step


Step 0/1● create the directory structure● add Symfony2 classloader as submodule● init and update submodule● (optional) create an empty class


Step 2● write the test with the smallest

amount of code you think it'snecessary


Step 3● add the Vertex class● add the Graph class● add an empty solve() method

for the algorithm class


Step 4● implement the solve method


Step 5● added all the methods

needed by the Dijkstra::solve()● need to implement Graph::calculatePotentials()


Step 6● a test is added for the Graph class


Step 7● calculatePotentials() is tested● half of our test-suite passes● switch back to the Dijkstra's test


Step 8● minor tweaks to make all the tests pass


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 Graphinto Dijkstra's class, we can delete the GraphTest


Step 10● since we like to be OO, we can connect

vertices through objects, and notarrays anymore


Step 11● we now need to fix the code which

uses vertices' connections as arrays


Step 12● the library seems pretty complete● PHPDoc is added


Step 13● Oooops, we forgot to test a scenario:

in Dijkstra's algorithm we need verticesconnected by positive distance

● a test is added, verifying an exceptionis raised through annotations


Step 14● implementation


Step 15● enter Mocking objects


Step 16● Dijkstra::getGraph() seems to be useless

so we probably don't need any Graph class


Step 17● removed Graph class


Step 18● some tests rely on it, so we need to

eliminate old references to Graph


Step 19● enter Data Providers


Step 20● what about calculating the path between

not-connected vertices?It should return null, so code is refactored


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

Alessandro Nadalin


odino.org


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@_odino_ #osidays

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REST in peace: tomorrow, 12.45

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@_odino_

Thank YOU!

Got units? @ Osidays 2011 India 11-20-2011

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