The Interleave Controller filters test samples through one at a time for each iteration through the test. This means
that if the Interleave Controller has a Web Test sub-controller within it, which in turn holds three URL's to be tested,
rather than serve up all three URL's during each run through the test, the Interleave Controller will instead serve up
the first URL during the first iteration through the test, the second URL during the second iteration, and the third one
during the third iteration. On the fourth iteration, the first URL will again be served, and so on.
An example of the usefulness of interleaving might be helpful. Let's say you have a search engine test that involves 3 steps. Step
one is always the same. Step two involves a URL request that follows a simple format, but the data can vary (think of a
search function - the request is always the same, except the actual search string can be different). Step three is also
always the same. If you wanted to test the search engine with, say, 10 different search strings, you could setup these
three steps and then repeat all three 10 times, modifying the second step in each to have a different search string. Or,
you could place the second step under an Interleave Controller, and put all 10 alternatives there. This would achieve the
same effect.