RuntimeError: The number of parameters does not match the number of
substitutions. on the assert_redirect_to line.
The point of TDD is to go beyond matching each line of code with an identical line of test. You should instead accept the redirection, render the target page, and then use assert_select to reach in for some artifact that shows your data is getting thru to the user.
Look up "integration tests", then add one for this scenario. And don't let the names fool you - Rails may claim to support functional, integration, and unit tests, but they are all just TDD tests. (Those things have strict QA definitions that we don't care about.)
The difference between the test categories is the avaliable "fixtures", or reusable support code. So integration tests will be able to follow you into the redirected page.
Any ideas?
Reduce :controller => "/users/profile" to just the name of your controller; either :users or :profile. Let the assertion figure out the rest.