private void registerFunctionOnServers() {
    function = new TestQueryFunction("queryFunction");
    server1.invoke(PRClientServerTestBase.class, "registerFunction", new Object[] {function});

    server2.invoke(PRClientServerTestBase.class, "registerFunction", new Object[] {function});

    server3.invoke(PRClientServerTestBase.class, "registerFunction", new Object[] {function});
  }
Test on PR on one server only using filter.
geode-core/src/distributedTest/java/org/apache/geode/cache/query/dunit/QueryUsingFunctionContextDUnitTest.java