Mocks.
Merge branch 'master' into feature/mock
Starting test refactor.
Continuing refactor.
More refactoring.
Working through test modules one at a time.
Updated test_helpers.
MOAR test cleanups.
Even more cleanup.
Standardize testcase naming.
Move mock to test libs.
Fix #482
Cleanup fixes.
Test shuffle.
More test cleanup.
Moar test fixes.
...
More cleanups.
Support for Expression-based joins when using aggregate_rows()

Joining on an Expression when using aggregate_rows() would cause an error because rel_for_model only handles Fields