Class BadFileLike

numpy/lib/tests/test_loadtxt.py:850–857

        # via the public interface (although maybe not impossible considering
        # the current "DataClass" backing).
        class BadFileLike:
            counter = 0

            def read(self, size):
                self.counter += 1
                if self.counter > 20:
                    raise RuntimeError("Bad bad bad!")
                return "1,2,3\n"

        with pytest.raises(RuntimeError, match="Bad bad bad!"):
            np.core._multiarray_umath._load_from_filelike(