private Execution createExecution(Searcher searcher) {
        return new Execution(chainedAsSearchChain(searcher), Execution.Context.createContextStub());
    }
Helper for testing with a rule base.
Replace subclassing of RuleBaseAbstractTestCase by this.

@author bratseth
container-search/src/test/java/com/yahoo/prelude/semantics/test/RuleBaseTester.java