We may have a solution, turns out the test name isn't limited or wrapped. By adding the ##vso command as a test, that will allow it to be picked up by Azure. As an example, in the test post-request;

pm.variables.set("testname","##vso[task.setvariable variable=MyReallyLongVariable]AndReallyLongValue"));
pm.test(pm.variables.get("testname"), () => {
    pm.expect(true).to.eq(true);
});