     func testNegatedStructureFail(){
         let source = "a"
         
-        for failure in validate(lowLevelResult: check(rule:singleLetterRule.newBehaviour(.structural(token: aToken), negated:true), on:source, includeAST: true), index: source.startIndex, errors: ["Undefined error at 1"], expectedResult: .failure, token: nil){
+        for failure in validate(lowLevelResult: check(rule:singleLetterRule.newBehaviour(.structural(token: aToken), negated:true), on:source, includeAST: true), index: source.startIndex, errors: ["Undefined error at 0"], expectedResult: .failure, token: nil){
             XCTFail(failure)
         }
     }

    
    func testNotScanFailure(){
        let source = "a"
        for failure in validate(lowLevelResult: check(rule:singleLetterRule.newBehaviour(negated:true), on:source), index: source.startIndex, errors: ["Undefined error at 1"], expectedResult: .failure){
            XCTFail(failure)
        }
    }

    func testNotLookaheadFailure(){
        //Look-ahead, positive, failure
        let source = "a"
        for failure in validate(lowLevelResult: check(rule:singleLetterRule.newBehaviour(negated:true,lookahead:true), on:source), index: source.startIndex, errors: ["Undefined error at 0"], expectedResult: .failure){
            XCTFail(failure)
        }
    }
