I found a previous thread that mentioned testing an RSS import using my test blog, but when I look under Account → Feeds → Edit feeds and cross-posting, I only have the option to import into my main blog. How do I get the option to import into the test blog?
When you add a feed on that feeds page, Micro.blog shows the currently selected blog. To change it, go to the Posts page and click the “…” to select the test blog. Then go back to the Edit Feeds page and that is the blog that it will default to.
(That feeds page really should have its own button to select a new blog, but hopefully this work-around helps for now.)