Python nosetest不能工作，但是可以使用matplotlib的@image_comparison直接运行它

Question

我有一个名为test_boxplot.py的测试脚本：

__author__ = 'olga'

from matplotlib.testing.decorators import image_comparison
import matplotlib.pyplot as plt
import numpy as np
import prettyplotlib as ppl
import os


@image_comparison(baseline_images=['boxplot'], extensions=['png'])
def test_boxplot():
    # Set the random seed for consistency
    np.random.seed(10)

    data = np.random.randn(8, 4)
    labels = ['A', 'B', 'C', 'D']

    fig, ax = plt.subplots()
    ppl.boxplot(ax, data, xticklabels=labels)
    # fig.savefig('%s/baseline_images/test_boxplot/boxplot.png' %
    #             os.path.dirname(__file__))


if __name__ == '__main__':
    import nose
    nose.runmodule(argv=['-s', '--with-doctest'])

如果我直接运行它，测试都会通过：

$ python test_boxplot.py
/Users/olga/workspace-git/matplotlib/lib/matplotlib/testing/decorators.py:288: UserWarning: test module run as script. guessing baseline image locations
  warnings.warn('test module run as script. guessing baseline image locations')
.
----------------------------------------------------------------------
Ran 1 test in 0.224s

OK

但是如果我用nosetests运行它，它会失败，出现这个奇怪的IndexError，它以matplotlib的@image_comparison装饰器的代码为中心：

$ nosetests test_boxplot.py
E
======================================================================
ERROR: Failure: IndexError (pop from empty list)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/usr/local/Cellar/python/2.7.6/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/nose/loader.py", line 286, in generate
    for test in g():
  File "/Users/olga/workspace-git/matplotlib/lib/matplotlib/testing/decorators.py", line 145, in test
    baseline_dir, result_dir = _image_directories(self._func)
  File "/Users/olga/workspace-git/matplotlib/lib/matplotlib/testing/decorators.py", line 296, in _image_directories
    assert mods.pop(0) == 'tests'
IndexError: pop from empty list

----------------------------------------------------------------------
Ran 1 test in 0.092s

FAILED (errors=1)

你知道可能发生了什么吗？

Answer 1

我认为问题是装饰器期望在主项目目录的子目录中使用“something.tests.”(通常是测试或更准确地说:测试模块必须以test开头)。这是_image_directories()中的代码

mods = module_name.split('.')
mods.pop(0) # <- will be the name of the package being tested (in
            # most cases "matplotlib")
assert mods.pop(0) == 'tests'
subdir = os.path.join(*mods)

在func.__module__ == '__main__'的情况下，_image_directories()有一些特殊的代码，所以您在第一种情况下看不到错误。