#vulnerable code 
                                @Test
    public void testFunctionsBasic() throws Exception {
        URL resource = getClass().getResource("/yaml/functions/functions_test_flow.sl");
        URI operation = getClass().getResource("/yaml/functions/functions_test_op.sl").toURI();
        Set<SlangSource> path = Sets.newHashSet(SlangSource.fromFile(operation));
        CompilationArtifact compilationArtifact = slang.compile(SlangSource.fromFile(resource.toURI()), path);

        Map<String, Serializable> userInputs = prepareUserInputs();
        Set<SystemProperty> systemProperties = prepareSystemProperties();

        // trigger ExecutionPlan
        RuntimeInformation runtimeInformation = triggerWithData(compilationArtifact, userInputs, systemProperties);

        Map<String, StepData> executionData = runtimeInformation.getTasks();

        StepData flowData = executionData.get(EXEC_START_PATH);
        StepData taskData = executionData.get(FIRST_STEP_PATH);
        Assert.assertNotNull("flow data is null", flowData);
        Assert.assertNotNull("task data is null", taskData);

        verifyFlowInputs(flowData);
        verifyTaskArguments(taskData);
        verifyTaskPublishValues(taskData);

        // verify 'get' function worked in result expressions
        Assert.assertEquals("Function evaluation problem in result expression", "FUNCTIONS_KEY_EXISTS", flowData.getResult());
    } 
                            #location 26 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                @Test
    public void testFunctionsBasic() throws Exception {
        URL resource = getClass().getResource("/yaml/functions/functions_test_flow.sl");
        URI operation = getClass().getResource("/yaml/functions/functions_test_op.sl").toURI();
        Set<SlangSource> path = Sets.newHashSet(SlangSource.fromFile(operation));
        CompilationArtifact compilationArtifact = slang.compile(SlangSource.fromFile(resource.toURI()), path);

        Map<String, Serializable> userInputs = prepareUserInputs();
        Set<SystemProperty> systemProperties = prepareSystemProperties();

        // trigger ExecutionPlan
        RuntimeInformation runtimeInformation = triggerWithData(compilationArtifact, userInputs, systemProperties);

        Map<String, StepData> executionData = runtimeInformation.getTasks();

        StepData flowData = executionData.get(EXEC_START_PATH);
        StepData taskData = executionData.get(FIRST_STEP_PATH);
        Assert.assertNotNull("flow data is null", flowData);
        Assert.assertNotNull("task data is null", taskData);

        verifyFlowInputs(flowData);
        verifyTaskArguments(taskData);
        verifyTaskPublishValues(taskData);
        verifyFlowOutputs(flowData);

        // verify 'get' function worked in result expressions
        Assert.assertEquals("Function evaluation problem in result expression", "FUNCTIONS_KEY_EXISTS", flowData.getResult());
    }