# Testing confusion **URL:** \ **Category:** Rails\ **Created:** [September 15, 2006, 7:13pm UTC](https://www.ruby-forum.com/t/testing-confusion/68827 "2006-09-15T19:13:03Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![stewbawka](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/a9adbd/32.png) [@stewbawka](https://www.ruby-forum.com/u/stewbawka)\ **Post date:** [September 15, 2006, 7:13pm UTC](https://www.ruby-forum.com/t/testing-confusion/68827/1 "2006-09-15T19:13:03Z")
ok, i’ve written a fairly feature rich rails app and right now i’m catching up with myself by writing the tests for the damned thing. currently getting the unit tests out of the way, but i have written one functional test also… here’s my problem… when i run rake test one of my test units flunks horribly with a bunch of exceptions of the type “RuntimeError: Called id for nil, which would mistakenly be 4 – if you really wanted the id of nil, use object\_id” … but when i run the test on its own it passes with flying colors… anybody know how this can be? i was under the impression that the tests are completely isolated from each other. thanks in advance, stuart ---
**Author:** ![stewbawka](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/a9adbd/32.png) [@stewbawka](https://www.ruby-forum.com/u/stewbawka)\ **Post date:** [September 15, 2006, 7:19pm UTC](https://www.ruby-forum.com/t/testing-confusion/68827/2 "2006-09-15T19:19:03Z")
Hi Stuart, Whenever I’ve had difference in behavior from running individual tests as opposed to the rake command they’ve usually been 1 of 2 things: 1. The database isn’t populated with the test data (you need to run rake at least once) 2. The fixture declarations aren’t correct. Make sure you’re loading all the related objects that you’re using in your tests and that the relationships are all correct. Hope that helps, -Michael ---
**Author:** ![stewbawka](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/a9adbd/32.png) [@stewbawka](https://www.ruby-forum.com/u/stewbawka)\ **Post date:** [September 15, 2006, 9:16pm UTC](https://www.ruby-forum.com/t/testing-confusion/68827/3 "2006-09-15T21:16:17Z")
When this has happened to me it has usually been one of 2-3 things: 1. Fixtures. If you don’t have fixtures :foos in your testcase then the changes you make to table foos won’t be rolled back when your test is done, leaving the database in a state you don’t expect 2. class variables, globals etc… These aren’t ‘reset’ after each test: You source files are loaded once and then all the tests are run. Slightly related is a problem we once had: we had some code with some external dependancy, and we forgot to have the appropriate require\_dependency ‘blah’ in the controller, and so when you ran this one test case you would get a failure. This library was also used in another controller, for which we had remembered the require\_dependancy, so if tests ran in the ‘right’ order then by the time the controller missing the require\_dependency ran the library had already been loaded and so the tests ran fine Hope that gives you some things to look at, Fred ---
**Author:** ![stewbawka](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/a9adbd/32.png) [@stewbawka](https://www.ruby-forum.com/u/stewbawka)\ **Post date:** [September 15, 2006, 10:07pm UTC](https://www.ruby-forum.com/t/testing-confusion/68827/4 "2006-09-15T22:07:19Z")
thanks for the input guys… so far still haven’t figured this one out… i did learn some things about testing though with your help. any other ideas? stuart ---
**Author:** ![stewbawka](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/a9adbd/32.png) [@stewbawka](https://www.ruby-forum.com/u/stewbawka)\ **Post date:** [September 18, 2006, 8:18pm UTC](https://www.ruby-forum.com/t/testing-confusion/68827/5 "2006-09-18T20:18:29Z")
That reminds of another issue I’ve seen before. By default each test runs inside it’s own database transaction which is rolled back at the end of the test. The corollary is that if your test commits that transaction then at the end of the test you won’t get that roll back. In addition to an actual commit statement there are (at least on mysql) a certain number of statements that cause an implicit commit (full list available on mysql’s website), these tend to be things like create table, drop index, etc… Any test containing one of those will screw up the transactional fixtures. You can work round this by turning off transactional fixtures for that test case. In my particular case, the offending table was essentially a scratch table, so my tests look something like def test\_foo do\_the\_thing\_implicitly\_comitting\_the\_transaction ActiveRecord::Base.connection.begin\_db\_transaction #do rest of test end The newly created transaction ensures that everything else will be rolled back at the end of the test Fred ---
**Author:** ![stewbawka](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/a9adbd/32.png) [@stewbawka](https://www.ruby-forum.com/u/stewbawka)\ **Post date:** [September 18, 2006, 7:56pm UTC](https://www.ruby-forum.com/t/testing-confusion/68827/6 "2006-09-18T19:56:42Z")
still trying to resolve this issue, but i have uncovered something interesting. the issue is definetly that 2 of the fixtures just aren’t getting along together. rake works fine with all test and either one of the culprits, but if the 2 are in the same test suite they start to complain. still not sure how to remedy this or even what’s going on… i tried changing the filenames and see if it would change the order that they ran in and possibly rescue the test suite from the errors… no luck i think i need more information about what exactly is going on between unit tests… i don’t have any globals, class variables etc… i’ve double checked that all fixtures that are needed are there (if i was missing one wouldn’t the ruby test/unit/test.rb fail??) really trying to get down to the bottom of this… any other ideas? thanks, stuart