Summary
The test queuedSingleNode , in blueocean-pipeline-api-impl, fails if run in such a way that a version of Jenkins core greater than 2.125 is in use. This can happen if the developer switches jenkins.version in pom.xml.

Here's what's going on.
1. This change introduced quotes around node labels.

2. You can also see here that the change went in around jenkins-2.125:

3. This assert fails, because it's looking for a string that doesn't contain those quotes.

4. Blue Ocean builds, done via something like mvn clean install, choose what version of Jenkins to run with via jenkins.version in pom.xml. And other approaches like the ATH, use the jenkins/jenkins:lts docker image. That docker image is running 2.121.3, meaning, it doesn't have the quotation marks change.

5. That means we'd have never seen this issue before. The test is written for an older version of Jenkins, and since Blue Ocean intentionally builds against an older version of Jenkins that predates the quotes change, the test passes.

I'm working on a different sort of Assert, which will allow the new way and the old way.