Thursday, February 25, 2016

Interesting use case example for `are` macro in Clojure test

I found an interesting use case for are in Clojure test.

You might have ever written a test for your data conversion logic. E.g.
  • Converting data pulled from third-party web service into your internal schema.
  • Converting data fetched from your database to more mobile friendly schema before sending out.
This is an example snippet of test for such a scenario.

convert-test1 shows the style I had been writing until recently. convert-test2 shows how using are making the test better.

Pros:
  • No more duplication of field values between input and output.
  • No more duplication between output schema and code under test schema.
  • It can be use as a document showing clearly how each individual field is mapped.
Cons:
An error message in convert-test1 is better. It shows clearly which field is wrong while convert-test2 throw out the whole problematic result data.

Updated: I have retested, are does report problem for an individual case as well.

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