Constraints are now declared final, so we cannot extend them anymore.
Hence, instead of extending PHPUnit\Framework\Constraint\IsEqual we
are just wrapping it into our constraint.
In PHPUnit 7.x and above, IsEqual->value became private and, as far
as our with exceptions class inherits from it, we cannot access to
that anymore.
So, in order to avoid that, we are overriding the constructor, capturing
the original value for own use and forgetting.
A more formal, alternative, solution would be to make our
exceptional class to inherit from Constraint and make the
class a pure dispatcher to different constraints, with IsEqual being
just one of them.
But we followed the easiest path here. Not ideal, but efective.
We often do isEqual tests but where a field, may have a single exception.
Ordinarily we can handle this easily by breaking the test down, but when
dealing with mocked objects we can only pass an instance of a
PHPUnit_Framework_Constraint, or a single value (which is cast to an
instance of PHPUnit_Framework_Constraint_IsEqual).
To deal with instances of time-based exception, we need to be able to
compare simple objects and classes where one or two values may be
different.
Eloy Lafuente (stronk7)