#vulnerable code 
                                @Test
    public void testValues() throws Exception {
        // compile
        URI resource = getClass().getResource("/yaml/formats/values_flow.sl").toURI();
        URI operation1 = getClass().getResource("/yaml/formats/values_op.sl").toURI();
        URI operation2 = getClass().getResource("/yaml/noop.sl").toURI();

        SlangSource dep1 = SlangSource.fromFile(operation1);
        SlangSource dep2 = SlangSource.fromFile(operation2);
        Set<SlangSource> path = Sets.newHashSet(dep1, dep2);
        CompilationArtifact compilationArtifact = slang.compile(SlangSource.fromFile(resource), path);

        // trigger
        Map<String, StepData> steps = prepareAndRun(compilationArtifact);

        // verify
        StepData flowData = steps.get(EXEC_START_PATH);
        StepData stepData = steps.get(FIRST_STEP_PATH);

        verifyExecutableInputs(flowData);
        verifyExecutableOutputs(flowData);
        verifyStepInputs(stepData);
        verifyStepPublishValues(stepData);
        verifySuccessResult(flowData);
    } 
                            #location 23 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                @Test
    public void testValues() throws Exception {
        // compile
        URI resource = getClass().getResource("/yaml/formats/values_flow.sl").toURI();
        URI operation1 = getClass().getResource("/yaml/formats/values_op.sl").toURI();
        URI operation2 = getClass().getResource("/yaml/noop.sl").toURI();

        SlangSource dep1 = SlangSource.fromFile(operation1);
        SlangSource dep2 = SlangSource.fromFile(operation2);
        Set<SlangSource> path = Sets.newHashSet(dep1, dep2);
        CompilationArtifact compilationArtifact = slang.compile(SlangSource.fromFile(resource), path);

        // trigger
        Map<String, StepData> steps = prepareAndRun(compilationArtifact);

        // verify
        StepData flowData = steps.get(EXEC_START_PATH);
        StepData stepData = steps.get(FIRST_STEP_PATH);

        verifyExecutableInputs(flowData);
        verifyExecutableOutputs(flowData);
        verifyStepInputs(stepData);
        verifySuccessResult(flowData);
    }