add README for tests

# How to run tests

The tests can be run with `python test.py` in this directory. But before running that, the script `test.py` must be modified according to your preferences.

## [Necessary] Specify a path to a verifier

Because a verifier is not a part of this repository, a path to a verifier must be specified according to your local installation. Setting the `default_verifier` variable should be enough.

## [Optional] Add a new verifier

To add a new verifier, a few things are needed.

* add a path to the verifier, as described above

* in the function `run_verifier`, add a command which runs the verifier

* in the function `get_verifier_result`, specify how to parse the verifier output

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    output_dir_c = os.path.join(script_file, "./output/c")

    llvm_as_path = "llvm-as-14"

    llvm2c_path = os.path.join(script_file, "../../tools/llvm2c/build/llvm2c") # LLVM IR to C decompiler

    # SPECIFY YOUR VERIFIER PATHS HERE

    symbiotic_path = os.path.join(script_file, "../../tools/symbiotic25/bin/symbiotic") # symbiotic path

    cbmc_path = "cbmc" # cbmc path

    default_verifier = symbiotic_path 

    name_filter = args.name_filter

    show_output = args.show_output

    if args.cbmc:

        verifier = cbmc_path

    else:

    if args.symbiotic:

        verifier = symbiotic_path

    else:

        verifier = default_verifier

    main(reverser_path, input_dir, output_dir_ll, output_dir_bc, output_dir_c, llvm_as_path, 

         verifier, llvm2c_path, name_filter, show_output, timeout_sec, sv_comp)