py.test由於缺少模塊而失敗

Question

我想編寫一個測試，但只有在安裝了nlopt模塊後，此測試纔會通過。由於這個模塊是可選，我想知道是否有辦法編寫一個測試，如果該模塊不存在，將不會阻止py.test完全失敗。在這一點上，py.test停止，因爲找不到nlopt模塊：

$ make test 
py.test --exitfirst tests/ 
============================================================= test session starts ============================================================= 
platform darwin -- Python 3.4.2 -- py-1.4.26 -- pytest-2.6.4 
collecting 0 items/1 errors 
=================================================================== ERRORS ==================================================================== 
_____________________________________________ ERROR collecting tests/unit/fem/test_simulation.py ______________________________________________ 
tests/unit/fem/test_simulation.py:5: in <module> 
    from hybrida.fem import Simulation, Step, Eigenvalue 
src/hybrida/__init__.py:4: in <module> 
    from . import geometry 
src/hybrida/geometry/__init__.py:3: in <module> 
    from . import distance 
src/hybrida/geometry/distance.py:9: in <module> 
    import nlopt 
E ImportError: No module named 'nlopt' 
--------------------------------------------------------------- Captured stdout --------------------------------------------------------------- 
nlopt does not seem to be installed. 
=========================================================== short test summary info =========================================================== 
ERROR tests/unit/fem/test_simulation.py 
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! Interrupted: stopping after 1 failures !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! 
=========================================================== 1 error in 0.67 seconds =========================================================== 
make: *** [test] Error 2 

我試圖在測試文件的開頭添加一個try-except塊，但這並沒有幫助：

try: 
    import nlopt 
    import numpy as np 

except ImportError: 
    print("""nlopt does not seem to be installed""") 

nlopt模塊用於我正在編寫測試的庫中。目前，如果找不到該模塊，該庫會引發異常。在文件的頂層使用該模塊：

try: 
    import nlopt 

except ImportError: 
    print("""\033[91m nlopt does not seem to be installed. Please install it by downloading nlopt, and installing it using 
     $ ./configure --enable-shared 
     $ make 
     $ make install 
     and adding /usr/local/lib/Python3.4/site-packages to the PYTHONPATH 
     (or wherever nlopt has been installed): 
     export PYTHONPATH=$PYTHONPATH:/usr/local/lib/Python3.4/site-packages 

     Note: although Homebrew provides nlopt, it does not install the Python interface.\033[0m""") 
    raise 

Answer 1

使用conditional import machinery pytest提供：

nlopt = pytest.importorskip('nlopt') 

把該行使用nlopt特定測試功能的內部（或在設置方法一組函數），它只會在不能進行導入時跳過這些函數。