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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Travis CI sporadically fails in control.tests.convert_test.TestConvert","articleBody":"Travis CI tests are failing in semi-random ways and generating the following error:\r\n\r\n```\r\nFAIL: testConvert (control.tests.convert_test.TestConvert)\r\nTest state space to transfer function conversion.\r\n----------------------------------------------------------------------\r\nTraceback (most recent call last):\r\n  File \"/home/travis/build/python-control/python-control/control/tests/convert_test.py\", line 86, in testConvert\r\n    ssTransformed = matlab.ss(tfOriginal)\r\n  File \"/home/travis/build/python-control/python-control/control/statesp.py\", line 1149, in ss\r\n    return tf2ss(sys)\r\n  File \"/home/travis/build/python-control/python-control/control/statesp.py\", line 1223, in tf2ss\r\n    return _convertToStateSpace(sys)\r\n  File \"/home/travis/build/python-control/python-control/control/statesp.py\", line 779, in _convertToStateSpace\r\n    num, den = sys._common_den()\r\n  File \"/home/travis/build/python-control/python-control/control/xferfcn.py\", line 821, in _common_den\r\n    % quad.imag.max()\r\nAssertionError: Quadratic has a nontrivial imaginary part: 1.06581e-14\r\n```\r\n\r\nThe error is not always present and re-running the build sometimes fixes it.  It appears the problem may be due to the way that random test cases are generated (although the seed is fixed in the unit test =\u003e not sure how we are getting different results on rebuild).","author":{"url":"https://github.com/murrayrm","@type":"Person","name":"murrayrm"},"datePublished":"2018-02-23T07:27:00.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":5},"url":"https://github.com/194/python-control/issues/194"}