difference between "nosetests test_x.py" and "nosetests test_x"?

[Roy Smith]

I have a trivial test file:

$ cat test_x.py

import test_common

def test_foo():

    pass

If I run "nosetests test_x.py", it runs fine.  If, however, I run "nosetests test_x", it fails when it tries to run the import (see below).  I don't understand what's happening here.

$ nosetests test_x

E

======================================================================

ERROR: Failure: ImportError (No module named test_common)

----------------------------------------------------------------------

Traceback (most recent call last):

  File "/home/roy/production/python/local/lib/python2.7/site-packages/nose/loader.py", line 390, in loadTestsFromName

    addr.filename, addr.module)

  File "/home/roy/production/python/local/lib/python2.7/site-packages/nose/importer.py", line 39, in importFromPath

    return self.importFromDir(dir_path, fqname)

  File "/home/roy/production/python/local/lib/python2.7/site-packages/nose/importer.py", line 86, in importFromDir

    mod = load_module(part_fqname, fh, filename, desc)

  File "/home/roy/songza/api2/test_x.py", line 1, in <module>

    import test_common

ImportError: No module named test_common

----------------------------------------------------------------------

Ran 1 test in 0.001s

FAILED (errors=1)