fuzztesting using ProcessBuilder

[hybrid tinsel]

(context: school assignment)

I've been provided with a program to test, and when messing around with it's inputs manually, I can make it error (example, index out of bounds)

However, when trying to crash it through ProcessBuilder (which was suggested as the way to build the fuzztester) I can't get a different output between crash/nocrash/ Everything looks identical. The exit code is always 1, the error stream is identical, I can't figure out a way to tell the difference between it resolving properly and not.

I'm sure that processbuilder can do this, but I just can't figure out what method I'm missing that gives this a distinct output.

Here's the code I'm using right now, I haven't done any fuzzing, just trying to get the error detection going first since nothing works without that.

import java.lang.ProcessBuilder;

public class testRunner {
    public static void  main(String[] args) {
        try {
            ProcessBuilder processBuilder = new ProcessBuilder("java", "PacketLab", "input.txt");
            Process process = processBuilder.start();
            process.waitFor();
            System.out.println("exit code: " + process.exitValue());
            System.out.println("errorStream: " + process.getErrorStream());
        }
        catch(Exception e) {
            System.out.println("caught error: " + e);
        }
    }
}```

 If I run this with valid inputs in input.txt, it outputs exactly the same exit code and errorStream as if I use invalid inputs in input.txt. But I know that if I manually run PacketLab with those inputs, it gives me an error, for example, the last time I did this, it gave this:
```Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: Index 1 out of bounds for length 1
        at PacketLab.process(PacketLab.java:130)
        at PacketLab.main(PacketLab.java:41)```

[vale kayak]

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[pearl stag]

in your PacketLab class, log the absolute path of the file, it's plausible it's reading the file from different dir than what you think

[hybrid tinsel]

im not supposed to change packetlab, but i assume you mean just for testing

i can alter the input txt and crash packetlab manually, so doesn't that mean its reading it from where i expect? or do you mean theres a chance my manual instance is reading from somewhere else than the instance pricessbuilder starts?

[odd moss]

Is PacketLab.class in the same directory as your test runner application?

and input.txt in the same directory?

Maybe take a look at the exception itself to find out why it happens