private static Execution newExecution(Searcher... searchers) {
        return new Execution(new SearchChain(new ComponentId("foo"), List.of(searchers)),
                             Execution.Context.createContextStub());
    }
Tests the internal rewriting of rank properties which happens in the query.prepare() call
(triggered by the exc.search call in the below).
container-search/src/test/java/com/yahoo/search/grouping/vespa/GroupingExecutorTestCase.java