We were showing only the ones being shown in the current page because
we were modifying `@investments` using a method which used
`@investments`, and we were calling that method twice.
There are many possible solutions: using a local variable to store the
result of the `investments` method, modifying `@investments` after
modifying `@investments_map_coordinates`, ... I've used the one which in
my humble opinion is a bit less fragile: not using `@investments` inside
the `investments` method. That way, the `investments` method will always
return the same result.
Note `stub_const("Budgets::InvestmentsController::PER_PAGE", 2)`
wouldn't work because `Budgets::InvestmentsController` isn't loaded when
that line is executed. So we need to load it. Instead of requiring the
file, using `#{Budgets::InvestmentsController}` seems to be an easier
solution.