def prange_tester(self, pyfunc, *args, **kwargs):
        """
        The `prange` tester
        This is a hack. It basically switches out range calls for prange.
        It does this by copying the live code object of a function
        containing 'range' then copying the .co_names and mutating it so
        that 'range' is replaced with 'prange'. It then creates a new code
        object containing the mutation and instantiates a function to contain
        it. At this point three results are created:
        1. The result of calling the original python function.
        2. The result of calling a njit compiled version of the original
            python function.
        3. The result of calling a njit(parallel=True) version of the mutated
           function containing `prange`.
        The three results are then compared and the `prange` based function's
        llvm_ir is inspected to ensure the scheduler code is present.

        Arguments:
         pyfunc - the python function to test
         args - data arguments to pass to the pyfunc under test

        Keyword Arguments:
         patch_instance - iterable containing which instances of `range` to
                          replace. If not present all instance of `range` are
                          replaced.
         scheduler_type - 'signed', 'unsigned' or None, default is None.
                           Supply in cases where the presence of a specific
                           scheduler is to be asserted.
         check_fastmath - if True then a check will be performed to ensure the
                          IR contains instructions labelled with 'fast'
         check_fastmath_result - if True then a check will be performed to
                                 ensure the result of running with fastmath
                                 on matches that of the pyfunc
         Remaining kwargs are passed to np.testing.assert_almost_equal


        Example:
            def foo():
                acc = 0
                for x in range(5):
                    for y in range(10):
                        acc +=1
                return acc

            # calling as
            prange_tester(foo)
            # will test code equivalent to
            # def foo():
            #     acc = 0
            #     for x in prange(5): # <- changed
            #         for y in prange(10): # <- changed
            #             acc +=1
            #     return acc

            # calling as
            prange_tester(foo, patch_instance=[1])
            # will test code equivalent to
            # def foo():
            #     acc = 0
            #     for x in range(5): # <- outer loop (0) unchanged
            #         for y in prange(10): # <- inner loop (1) changed
            #             acc +=1
            #     return acc

        """
        patch_instance = kwargs.pop('patch_instance', None)
        check_fastmath = kwargs.pop('check_fastmath', False)
        check_fastmath_result = kwargs.pop('check_fastmath_result', False)

        pfunc = self.generate_prange_func(pyfunc, patch_instance)

        # Compile functions
        # compile a standard njit of the original function
        sig = tuple([numba.typeof(x) for x in args])
        cfunc = self.compile_njit(pyfunc, sig)

        # compile the prange injected function
        with warnings.catch_warnings(record=True) as raised_warnings:
            warnings.simplefilter('always')
            cpfunc = self.compile_parallel(pfunc, sig)

        # if check_fastmath is True then check fast instructions
        if check_fastmath:
            self.assert_fastmath(pfunc, sig)

        # if check_fastmath_result is True then compile a function
        # so that the parfors checker can assert the result is ok.
        if check_fastmath_result:
            fastcpfunc = self.compile_parallel_fastmath(pfunc, sig)
            kwargs = dict({'fastmath_pcres': fastcpfunc}, **kwargs)

        self.check_parfors_vs_others(pyfunc, cfunc, cpfunc, *args, **kwargs)
        return raised_warnings

        The `prange` tester
        This is a hack. It basically switches out range calls for prange.
        It does this by copying the live code object of a function
        containing 'range' then copying the .co_names and mutating it so
        that 'range' is replaced with 'prange'. It then creates a new code
        object containing the mutation and instantiates a function to contain
        it. At this point three results are created:
        1. The result of calling the original python function.
        2. The result of calling a njit compiled version of the original
            python function.
        3. The result of calling a njit(parallel=True) version of the mutated
           function containing `prange`.
        The three results are then compared and the `prange` based function's
        llvm_ir is inspected to ensure the scheduler code is present.

        Arguments:
         pyfunc - the python function to test
         args - data arguments to pass to the pyfunc under test

        Keyword Arguments:
         patch_instance - iterable containing which instances of `range` to
                          replace. If not present all instance of `range` are
                          replaced.
         scheduler_type - 'signed', 'unsigned' or None, default is None.
                           Supply in cases where the presence of a specific
                           scheduler is to be asserted.
         check_fastmath - if True then a check will be performed to ensure the
                          IR contains instructions labelled with 'fast'
         check_fastmath_result - if True then a check will be performed to
                                 ensure the result of running with fastmath
                                 on matches that of the pyfunc
         Remaining kwargs are passed to np.testing.assert_almost_equal


        Example:
            def foo():
                acc = 0
                for x in range(5):
                    for y in range(10):
                        acc +=1
                return acc

            # calling as
            prange_tester(foo)
            # will test code equivalent to
            # def foo():
            #     acc = 0
            #     for x in prange(5): # <- changed
            #         for y in prange(10): # <- changed
            #             acc +=1
            #     return acc

            # calling as
            prange_tester(foo, patch_instance=[1])
            # will test code equivalent to
            # def foo():
            #     acc = 0
            #     for x in range(5): # <- outer loop (0) unchanged
            #         for y in prange(10): # <- inner loop (1) changed
            #             acc +=1
            #     return acc

        
numba/tests/test_parfors.py