Error when running single test case

[ducminhgd]

It's OK if choose "run all" or "run selected" with the script file selected, but when I choose a test case then click "run selected", an error occured:

Traceback (most recent call last):
File "manage.py", line 10, in
execute_from_command_line(sys.argv)
File "/usr/local/lib/python2.7/dist-packages/django/core/management/init.py", line 399, in execute_from_command_line
utility.execute()
File "/usr/local/lib/python2.7/dist-packages/django/core/management/init.py", line 392, in execute
self.fetch_command(subcommand).run_from_argv(self.argv)
File "/usr/local/lib/python2.7/dist-packages/django/core/management/commands/test.py", line 50, in run_from_argv
super(Command, self).run_from_argv(argv)
File "/usr/local/lib/python2.7/dist-packages/django/core/management/base.py", line 242, in run_from_argv
self.execute(_args, *_options.dict)
File "/usr/local/lib/python2.7/dist-packages/django/core/management/commands/test.py", line 71, in execute
super(Command, self).execute(_args, *_options)
File "/usr/local/lib/python2.7/dist-packages/django/core/management/base.py", line 285, in execute
output = self.handle(_args, *_options)
File "/usr/local/lib/python2.7/dist-packages/django/core/management/commands/test.py", line 88, in handle
failures = test_runner.run_tests(test_labels)
File "/usr/local/lib/python2.7/dist-packages/django/test/runner.py", line 144, in run_tests
suite = self.build_suite(test_labels, extra_tests)
File "/usr/local/lib/python2.7/dist-packages/django/test/runner.py", line 63, in build_suite
tests = self.test_loader.loadTestsFromName(label)
File "/usr/lib/python2.7/unittest/loader.py", line 91, in loadTestsFromName
module = import('.'.join(parts_copy))
ImportError: No module named myapp