如何检查单位测试中的值是否为nan？

Question

我有功能，有时返回NaNs float('nan')（我不使用numpy）。

如何为它编写一个测试，因为

assertEqual(nan_value, float('nan')) 

就像float('nan') == float('nan')始终为false。有没有像assertIsNan？我找不到任何关于它...

Answer 1

我想出了

assertTrue(math.isnan(nan_value)) 

Answer 2

math.isnan(x)将引发TypeError如果x既不是float也不是Real。

这是更好地使用这样的事情：

import math 


class NumericAssertions: 
    """ 
    This class is following the UnitTest naming conventions. 
    It is meant to be used along with unittest.TestCase like so : 
    class MyTest(unittest.TestCase, NumericAssertions): 
     ... 
    It needs python >= 2.6 
    """ 

    def assertIsNaN(self, value, msg=None): 
     """ 
     Fail if provided value is not NaN 
     """ 
     standardMsg = "%s is not NaN" % str(value) 
     try: 
      if not math.isnan(value): 
       self.fail(self._formatMessage(msg, standardMsg)) 
     except: 
      self.fail(self._formatMessage(msg, standardMsg)) 

    def assertIsNotNaN(self, value, msg=None): 
     """ 
     Fail if provided value is NaN 
     """ 
     standardMsg = "Provided value is NaN" 
     try: 
      if math.isnan(value): 
       self.fail(self._formatMessage(msg, standardMsg)) 
     except: 
      pass 

然后可以使用self.assertIsNaN()和self.assertIsNotNaN()。