Could you explain why this program runs?

[fl]

On Thursday, June 25, 2015 at 8:20:52 AM UTC-7, fl wrote:
> Hi,
> 
> I download and install pyPDF2 library online. It says the test can run by:
> 
> 
> python -m unittest Tests.tests
> 
> 
> tests.py is under folder PyPDF2-master\Tests\
> 
> 
> The above command line does run and give output message, but I don't 
> understand why it run after I read tests.py:
> 
> 
> ///////////////////////////////
> import os, sys, unittest
> 
> # Configure path environment
> TESTS_ROOT = os.path.abspath(os.path.dirname(__file__))
> PROJECT_ROOT = os.path.dirname(TESTS_ROOT)
> RESOURCE_ROOT = os.path.join(PROJECT_ROOT, 'Resources')
> 
> sys.path.append(PROJECT_ROOT)
> 
> # Test imports
> import unittest
> from PyPDF2 import PdfFileReader
> 
> 
> class PdfReaderTestCases(unittest.TestCase):
> 
> 	def test_PdfReaderFileLoad(self):
> 		'''	Test loading and parsing of a file. Extract text of the file and compare to expected
> 			textual output. Expected outcome: file loads, text matches expected.
> 		'''
> 		with open(os.path.join(RESOURCE_ROOT, 'crazyones.pdf'), 'rb') as inputfile:
> 			
> 			# Load PDF file from file
> 			ipdf = PdfFileReader(inputfile)
> 			ipdf_p1 = ipdf.getPage(0)
> 			
> 			# Retrieve the text of the PDF
> 			pdftext_file = open(os.path.join(RESOURCE_ROOT, 'crazyones.txt'), 'r')
> 			pdftext = pdftext_file.read()
> 			ipdf_p1_text = ipdf_p1.extractText()
> 			
> 			# Compare the text of the PDF to a known source
> 			self.assertEqual(ipdf_p1_text.encode('utf-8', errors='ignore'), pdftext,
> 				msg='PDF extracted text differs from expected value.\n\nExpected:\n\n%r\n\nExtracted:\n\n%r\n\n'
> 					% (pdftext, ipdf_p1_text.encode('utf-8', errors='ignore')))
> //////////////////////////////////////
> 
> It only gives a class PdfReaderTestCases() substantiation. I have read
> usage on class, but I have not found the answer.
> Can you help me on why the command line can run the test?
> 
> Thanks,

Thanks for reading. I make it out that it is a feature of unittest module.