On Friday, September 16, 2011 3:12:49 PM UTC-4, Brian Hurt wrote: > > > > On Thu, Sep 15, 2011 at 6:42 AM, Chris Perkins <chrispe...@gmail.com>wrote: > >> On Wednesday, September 14, 2011 11:19:13 AM UTC-4, Brian Hurt wrote: >>> >>> Say I have two name spaces, A and B, with A depending on B. I want to >>> test namespace A, replacing module B with a mock B for testing purposes- >>> preferably without having to load B at all (B sucks in a bunch of stuff, >>> like dependencies on databases and external web sites and etc. that I don't >>> want to deal with in testing). What is the easy, clojure-approved, >>> mechanism for doing this? I tried: >>> >>> How *should* I structure this code for testing? I was assuming the > natural way to do this is to make A, B, and C separate name spaces but maybe > this is wrong. > > The problem isn't just *writing* the code- I need to be able to change this > code later, and have some assurance it still works. So "load it up into a > repl and play with it" isn't a viable solution. > > Or is clojure code just not testable/maintainable? > > Brian > > I don't have a detailed answer because I haven't done much mocking myself, but I'm confident that it's possible. The reason for my confidence is that references from one namespace to another live in Vars, which are mutable.
Here's a very simple example: I made a namespace "a" containing a function "a-fn", which just calls b-fn in namespace b. Then I created a "mock-b" that defines a different b-fn. user=> (require 'a) nil user=> (a/a-fn) "real b" user=> (require 'mock-b) nil user=> (alter-var-root #'b/b-fn (constantly mock-b/b-fn)) #<mock_b$b_fn mock_b$b_fn@1e1be92> user=> (a/a-fn) "mock b" Note that the behavior of a-fn has been altered at runtime. I can imagine a mocking utility that, given a namespace (eg: "b"), and a mock namespace (eg: "mock-b"), would go through the vars in mock-b and call alter-var-root on all the matching vars in b before calling a test suite. In fact, I wouldn't be surprised at all to find this on github somewhere. Not much detail there, but I hope this helps somewhat. - Chris user=> -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en
