Take the 2-minute tour ×
Programmers Stack Exchange is a question and answer site for professional programmers interested in conceptual questions about software development. It's 100% free, no registration required.

Consider a text index such as a suffix tree or a suffix array supporting Count queries (number of occurrences of a pattern) and Locate queries (the positions of all the occurrences of a pattern) over a given text. How would you go about unit testing such a class ?

What I have in mind is to generate a big random string then extract a random substring from this big string and compare the results of both queries with naive implementations (such as string::find). Another idea I have is to find the most frequent substring of length l appearing in the original string (using perhaps a naive method) and use these substrings for testing the index.

This isn't the best way, so what would be a good design of the unit tests for a text index ?

In case it matters, this is in C++ using google test.

share|improve this question
add comment

1 Answer

up vote 3 down vote accepted

The random generated big string can be a nice addition to test the cases that you did not think of. To make it effective you would need to run it several times which slows down your unit testing suite, so you need to find a balance between the number of times you run the test and how big you would make the string.

I would still create a normal test set with a given input for which you know what the answer is.

  • a test for zero occurrences
  • a test for a random number of occurrences
  • a test for an occurrence in the first element
  • a test for an occurrence in the last element
  • a test for case sensitive
  • a test with an empty tree or array
  • a test for a tree or array with exactly one element
  • tests for any other functional requirements you might have (escape characters, line endings, ignoring white space, concurrent use, exception handling, more occurrences than your counter can hold)

Hope this helps.

share|improve this answer
    
I don't think those Assertions is enough for Count queries & Locate queries. So here we have to utilize Mocks and Stubs. –  Md. Mahbubur R. Aaman Oct 5 '12 at 6:56
    
@MahbuburRAaman: What do you want to mock? The index is being tested and it does not have any dependencies! –  Jan Hudec Oct 5 '12 at 7:54
    
@JanHudec,Yes you are right. I think KeesDijk answer is better here. So i removed my answer from here. –  Md. Mahbubur R. Aaman Oct 5 '12 at 8:22
add comment

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.