How to test order of Pages in Wagtail?

Question

I have a Wagtail site and I have a parent/child structure between a couple of page types:

class FrontPage(Page):
    subpage_types = ["InnerPage"]

    def get_next_page(self):
        return self.get_children().live().first()

class InnerPage(Page):
    parent_page_types = ["FrontPage"]

    def get_next_page(self):
        return self.get_next_siblings().live().first()

The Admin user can drag the InnerPages into their chosen order in the Wagtail Admin, which is great. FrontPage.get_children() then fetches the inner pages in that order, and the get_next_page() methods return the next pages in the same order.

I'd like to write tests to check that the get_next_page() methods do return the correct page. But I can't work out how to assign an order to pages when creating them for tests. I can see that when doing the SQL queries Wagtail orders by wagtailcore_page.path, but I'm not sure how to affect this when programmatically creating InnerPage objects.