The first item is the top result, because the search term “test” appears more frequently (5×), compared to the second item, in which the search terms appear only twice. Lunr uses the Okapi BM25 scoring algorithm for sorting search results by relevance, as described here.
As a reminder, by adding a handful of extra characters to your search expression, you can get the exact behavior that you want (e.g., >+micro* +test*). But I do understand that the feature request here proposes that this should be the default search behavior, and that’s fine.
There is another feature request for this, which you may wish to support: