Ruby on Rails Solving a No method Error

I'm currently going through Hartl's Ruby on Rails tutorial and I've come to a roadbloack with a failing test that I don't know how to get to pass. All of the previous tests through chapter 11 have ran correctly so I was hoping some one could help me interpret the errors.

Running:

bundle exec rake test

Gives me this

45 runs, 0 assertions, 0 failures, 45 errors, 0 skips

The first six errors are similar to this:

1) Error:
MicropostTest#test_should_be_valid:
ActiveRecord::Fixture::FormatError: ActiveRecord::Fixture::FormatError

And the rest of the errors follow this pattern:

7) Error:
UsersEditTest#test_unsuccessful_edit:
ActiveRecord::Fixture::FormatError: ActiveRecord::Fixture::FormatError


Error:
UsersEditTest#test_unsuccessful_edit:
NoMethodError: undefined method `each' for nil:NilClass

I'm not sure what an undefined method for a nil class would mean. If I need to post any more of my code/errors please let me know. Any help is appreciated. Thanks!