You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: test_buffer.rs
    path of file: ./repos/pyo3/tests
    
    the code of the file until where you have to start completion: #![cfg(feature = "macros")]
#![cfg(any(not(Py_LIMITED_API), Py_3_11))]

use pyo3::{buffer::PyBuffer, exceptions::PyBufferError, ffi, prelude::*};
use std::{
    ffi::CStr,
    os::raw::{c_int, c_void},
    ptr,
};

#[macro_use]
#[path = "../src/tests/common.rs"]
mod common;

enum TestGetBufferError {
    NullShape,
    NullStrides,
    IncorrectItemSize,
    IncorrectFormat,
    IncorrectAlignment,
}

#[pyclass]
struct TestBufferErrors {
    buf: Vec<u32>,
    error: Option<TestGetBufferError>,
}

#[pymethods]
impl TestBufferErrors {
    unsafe fn __getbuffer__(
        slf: PyRefMut<'_, Self>,
        view: *mut ffi::Py_buffer,
        flags: c_int,
    ) -> PyResult<()> {
        if view.is_null() {
            return Err(PyBufferError::new_err("View is null"));
        }

        if (flags & ffi::PyBUF_WRITABLE) == ffi::PyBUF_WRITABLE {
            return Err(PyBufferError::new_err("Object is not writable"));
        }

        let bytes = &slf.buf;

        (*view).buf = bytes.as_ptr() as *mut c_void;
        (*view).len = bytes.len() as isize;
        (*view).readonly = 1;
        (*view).itemsize = std::mem::size_of::<u32>() as isize;

        let msg = CStr::from_bytes_with_nul(b"I\0").unwrap();
        (*view).format = msg.as_ptr() as *mut _;

        (*view).ndim = 1;
        (*view).shape = &mut (*view).len;

        (*view).strides = &mut (*view).itemsize;

    
fn test_get_buffer_errors() {
    Python::with_gil(|py| {
        let instance = Py::new(
            py,
            TestBufferErrors {
                buf: vec![0, 1, 2, 3],
                error: None,
            },
        )
        .unwrap();

        assert!(PyBuffer::<u32>::get_bound(instance.bind(py)).is_ok());

        instance.borrow_mut(py).error = Some(TestGetBufferError::NullShape);
        assert_eq!(
            PyBuffer::<u32>::get_bound(instance.bind(py))
                .unwrap_err()
                .to_string(),
            "BufferError: shape is null"
        );

        instance.borrow_mut(py).error = Some(TestGetBufferError::NullStrides);
        assert_eq!(
            PyBuffer::<u32>::get_bound(instance.bind(py))
                .unwrap_err()
                .to_string(),
            "BufferError: strides is null"
        );

        instance.borrow_mut(py).error = Some(TestGetBufferError::IncorrectItemSize);
        assert_eq!(
            PyBuffer::<u32>::get_bound(instance.bind(py))
                .unwrap_err()
                .to_string(),
            "BufferError: buffer contents are not compatible with u32"
        );

        instance.borrow_mut(py).error = Some(TestGetBufferError::IncorrectFormat);
        assert_eq!(
            PyBuffer::<u32>::get_bound(instance.bind(py))
                .unwrap_err()
                .to_string(),
            "BufferError: buffer contents are not compatible with u32"
        );

        instance.borrow_mut(py).error = Some(TestGetBufferError::IncorrectAlignment);
        assert_eq!(
            PyBuffer::<u32>::get_bound(instance.bind(py))
                .unwrap_err()
                .to_string(),
            "BufferError: buffer contents are insufficiently aligned for u32"
        );
    });
}