Could you explain why this program runs?

[fl]

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,