[Activewarehouse-discuss] unit testing a control file

[Thibaut Barrère]

Hi,

here's my first and very raw (but quite successful) attempt at writing an
automated test for a real .ctl file, without requiring any modifications to
the .ctl file itself nor to AW-ETL.

The idea here is to mock the sources and destinations of a real .ctl file: I
replace all the sources by one mock source (eg: array of hashes), and
replace all the destinations by one, on which I assert to see if the
requirements are met. The connection to :etl_execution and the job creation
are also mocked, to avoid a database dependency and focus on the transforms.

With the plumbing removed, the test can be written:

describe "test.ctl" do
  it "should store :first_name + :last_name under :name" do
    load 'test.ctl', [ {:first_name => 'john',:last_name => 'barry'} ]
    @destination.should_receive(:write).with( { :first_name => 'john',
:last_name => 'barry', :name => 'john barry' } )
  end
end

This specification is written with RSpec and takes benefits of the mocking
abilities it provides (will be very practical to mock dimensions foreign-key
look-ups as well).
The plumbing was surprisingly easy to write, although it definitely requires
polishing (for instance, running two tests in a row won't work today!).
I think it would be reasonably easy to make AW-ETL more test-friendly by
refactoring some areas in order to remove part or all of the plumbing I
wrote to get this to work.

What do you think ?

cheers

Thibaut
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