While looking into another issue, I found two issues related to our node-query tests, specifically here: https://github.com/puppetlabs/puppetdb/blob/master/test/puppetlabs/puppetdb/http/nodes_test.clj#L65. There are tests in that namespace that actually generate incorrect SQL, I see a stacktrace in standard error, but the error isn't returned and PuppetDB is actually responding with a 200 and an empty body. The empty body causes the doseq above to be skipped, and since the response is 200, the test runs successfully, even though there was a failure and no results were returned.
We should also look into our bad handling of this failed query. Ideally it should be returning a 4xx error, but certainly shouldn't return a 200.