`allow_value` matcher is, of course, concerned with setting values on a
particular attribute on a particular record, and then checking that the
record is valid after doing so. That comes with a caveat: if the
attribute is overridden in such a way so that the same value going into
the attribute isn't the same value coming out of it, then `allow_value`
will balk -- it'll say, "I can't do that because that changes how I
work."
That's all well and good, but what the attribute intentionally changes
incoming values? ActiveRecord's typecasting behavior, for instance,
would trigger such an exception. What if the developer needs a way to
get around this? This is where `ignoring_interference_by_writer` comes
into play. You can tack it on to the end of the matcher, and you're free
to go on your way.
So, prior to this commit you could already apply it to `allow_value`,
but now in this commit it also works on any other matcher.
But, one little thing: sometimes using this qualifier isn't going to
work. Perhaps you or something else actually *is* overriding the
attribute to change incoming values in a specific way, and perhaps the
value that comes out makes the record fail validation, and there's
nothing you can do about it. So in this case, even if you're using
`ignoring_interference_by_writer`, we want to inform you about what the
attribute is doing -- what the input and output was. And so we do.
* It changes shoulda-matchers to allow the integration with multiple
libraries like active_model and active_record.
For example, in a non Rails project isn't possible to use both
validate_presence_of and validate_uniqueness_of matchers, because they
are from different libraries (one from active_model and the other from
active_record respectively).
This change allow the integration with multiple libraries. fixes#710
