---
title: testing your tests
teaser:
tags: web,rails,testing
author: Jared Carroll
published_on: 2007-11-01
---

Recently I was taking a look at my tests and noticed some things.  I've been
writing tests for my tests without knowing it.

Here's one I commonly do when testing the ordering of results from an
`ActiveRecord` class side finder.

This is wrong:

    def test_should_find_all_posts_ordered_by_most_recent_first_when_sent_recent
      posts = Post.recent
      posts.each_with_index do |each, index|
        if posts[index.succ]
          assert each.created_on >= posts[index.succ].created_on
        end
      end
    end

The problem with this test is that `Post#recent` could return an empty `Array`,
then `#each_with_index` would not run and no assertions would be run but the
test would still pass.

Rewrite:

    def test_should_find_all_posts_ordered_by_most_recent_first_when_sent_recent
      posts = Post.recent
      assert ! posts.empty?
      posts.each_with_index do |each, index|
        if posts[index.succ]
          assert each.created_on >= posts[index.succ].created_on
        end
      end
    end

Better.

Now we `#assert` that the collection returned from `Post#recent` is at least not
`#empty?`  However this test can still pass without executing 1 assertion
because in order to test ordering you need at least 2 objects.

Rewrite:

    def test_should_find_all_posts_ordered_by_most_recent_first_when_sent_recent
      posts = Post.recent
      assert ! posts.empty?
      assert posts.size >= 2
      posts.each_with_index do |each, index|
        if posts[index.succ]
          assert each.created_on >= posts[index.succ].created_on
        end
      end
    end

Now its good.

There's **no** way this test will pass without testing that the collection of
`posts` found by `Post#recent` is ordered by most recent first.