Python：编写用于控制台打印的单元测试

您可以通过临时重定向

sys.stdout

StringIO

import StringIOimport sysdef foo(inStr):    print "hi"+inStrdef test_foo():    capturedOutput = StringIO.StringIO()          # Create StringIO object    sys.stdout = capturedOutput        #  and redirect stdout.    foo('test')  # Call unchanged function.    sys.stdout = sys.__stdout__        # Reset redirect.    print 'Captured', capturedOutput.getvalue()   # Now works as before.test_foo()

该程序的输出为：

Captured hitest

说明重定向成功捕获了输出，并且您能够将输出流还原到开始捕获之前的状态。

请注意，上面的代码针对Python 2.7，如问题所示。Python 3稍有不同：

import ioimport sysdef foo(inStr):    print ("hi"+inStr)def test_foo():    capturedOutput = io.StringIO()       # Create StringIO object    sys.stdout = capturedOutput          #  and redirect stdout.    foo('test')    # Call function.    sys.stdout = sys.__stdout__          # Reset redirect.    print ('Captured', capturedOutput.getvalue())   # Now works as before.test_foo()