Those are assertions that I really do miss from the standard
`ActiveSupport::TestCase`. Think of those as a more general version of
`assert_difference` and `assert_no_difference` (those can be implemented
by assert_changes, should this change be accepted).
Why do we need those? They are useful when you want to check a
side-effect of an operation. `assert_difference` do cover a really
common case, but we `assert_changes` gives us more control. Having a
global error flag? You can test it easily with `assert_changes`. In
fact, you can be really specific about the initial state and the
terminal one.
```ruby
error = Error.new(:bad)
assert_changes -> { Error.current }, from: nil, to: error do
expected_bad_operation
end
```
`assert_changes` follows `assert_difference` and a string can be given
for evaluation as well.
```ruby
error = Error.new(:bad)
assert_changes 'Error.current', from: nil, to: error do
expected_bad_operation
end
```
Check out the test cases if you wanna see more examples.
🍻
With this we can perform new assertions on the returned value without having
to cache it with an outer variable or wrapping all subsequent assertions inside
the `assert_difference` block.
Before:
```
post = nil
assert_difference -> { Post.count }, 1 do
Post.create
end
assert_predicate post, :persisted?
```
Now:
```
post = assert_difference -> { Post.count } do
Post.create
end
assert_predicate post, :persisted?
```
Goals:
1. Default to :random for newly generated applications
2. Default to :sorted for existing applications with a warning
3. Only show the warning once
4. Only show the warning if the app actually uses AS::TestCase
Fixes#16769
+ Namespace changes, overhaul of runners.
+ Internal ivar name changes
- Removed a logger globally applied to tests that spew everywhere?!?
+ Override Minitest#__run to sort tests by name.
+ Reworked testing isolation to work with the new cleaner architecture.
- Removed a bunch of tests that just test minitest straight up. I think these changes were all merged to minitest 4 a long time ago.
- Minor report output differences.
Neither Test::Unit nor MiniTest rescue exceptions like Interrupt or
NoMemoryError, but ActiveSupport::Testing::SetupAndTeardown#run which
overrides MiniTest::Unit::TestCase#run rescues them.
Rescuing an Interrupt exception is annoying, because it means when you
are running a lot of tests e.g. when running one of the rake test tasks,
you cannot break out using ctrl-C.
Rescuing exceptions like NoMemoryError is foolish, because the most
sensible thing to happen is for the process to terminate as soon as
possible.
This solution probably needs some finessing e.g. I'm not clear whether
the assumption is that only MiniTest is supported. Also early versions
of MiniTest did not have this behaviour. However, hopefully it's a
start.
Integrating with Test::Unit & MiniTest has always been a pain. It would
be great if both of them provided sensible extension points for the kind
of things that both Rails and Mocha want to do.
