After we upgraded to QUnit 1.23.1, we gained support for
assert.expect(). This allows us to guard against any race conditions
within tests, because now expect() will be linked to the specific test
instead of the current running test.
Now we are using `jQuery.noConflict()` in tests, so it should be
slightly easier to detect when this happens next time. Tests just
need to be written for the component.
This closes https://github.com/select2/select2/issues/2985.
`selectOnClose` is a new option which works very much like the old
`selectOnBlur` option. When the `close` event is triggered, the
highlighted result is automatically selected. This is useful for
single selects, which is where it is designed to be used, but it
can also be used on multiple selects.
This also adds tests to verify that this works in the future.
During the creation of the test, we noticed that we were missing a
mock container that could be used for triggering events. One was
created and a general mock JS file was created to hold any future
mocks for tests.
