Add test_fetcher

Add unit test for requests_fetcher.py

Signed-off-by: Teodora Sechkova <tsechkova@vmware.com>

tests/test_fetcher.py

@@ -0,0 +1,119 @@
+#!/usr/bin/env python
+
+"""
+<Program>
+  test_download.py
+
+<Author>
+  Teodora Sechkova tsechkova@vmware.com
+
+<Started>
+  December 18, 2020.
+
+<Copyright>
+  See LICENSE-MIT OR LICENSE for licensing information.
+
+<Purpose>
+  Unit test for RequestsFetcher.
+"""
+
+import logging
+import os
+import io
+import sys
+import unittest
+import tempfile
+
+import tuf
+import tuf.exceptions
+import tuf.fetcher
+import tuf.unittest_toolbox as unittest_toolbox
+
+from tests import utils
+
+
+logger = logging.getLogger(__name__)
+
+
+class TestFetcher(unittest_toolbox.Modified_TestCase):
+  def setUp(self):
+    """
+    Create a temporary file and launch a simple server in the
+    current working directory.
+    """
+
+    unittest_toolbox.Modified_TestCase.setUp(self)
+
+    # Making a temporary file.
+    current_dir = os.getcwd()
+    target_filepath = self.make_temp_data_file(directory=current_dir)
+    self.target_fileobj = open(target_filepath, 'r')
+    self.file_contents = self.target_fileobj.read()
+    self.file_length = len(self.file_contents)
+
+    # Launch a SimpleHTTPServer (serves files in the current dir).
+    self.server_process_handler = utils.TestServerProcess(log=logger)
+
+    rel_target_filepath = os.path.basename(target_filepath)
+    self.url = 'http://localhost:' \
+        + str(self.server_process_handler.port) + '/' + rel_target_filepath
+
+    # Create a temporary file where the target file chunks are written
+    # during fetching
+    self.temp_file = tempfile.TemporaryFile()
+    self.fetcher = tuf.fetcher.RequestsFetcher()
+
+
+  # Stop server process and perform clean up.
+  def tearDown(self):
+    unittest_toolbox.Modified_TestCase.tearDown(self)
+
+    # Cleans the resources and flush the logged lines (if any).
+    self.server_process_handler.clean()
+
+    self.target_fileobj.close()
+    self.temp_file.close()
+
+
+  # Test: Normal case.
+  def test_fetch(self):
+
+    for chunk in self.fetcher.fetch(self.url, self.file_length):
+        self.temp_file.write(chunk)
+
+    self.temp_file.seek(0)
+    temp_file_data = self.temp_file.read().decode('utf-8')
+    self.assertEqual(self.file_contents, temp_file_data)
+    self.assertEqual(self.file_length, len(temp_file_data))
+
+
+  # Test if fetcher downloads file up to a required length
+  def test_fetch_restricted_length(self):
+    for chunk in self.fetcher.fetch(self.url, self.file_length-4):
+        self.temp_file.write(chunk)
+
+    self.temp_file.seek(0, io.SEEK_END)
+    self.assertEqual(self.temp_file.tell(), self.file_length-4)
+
+
+  # Test if fetcher does not downlad more than actual file length
+  def test_fetch_upper_length(self):
+    for chunk in self.fetcher.fetch(self.url, self.file_length+4):
+        self.temp_file.write(chunk)
+
+    self.temp_file.seek(0, io.SEEK_END)
+    self.assertEqual(self.temp_file.tell(), self.file_length)
+
+
+  # Test incorrect URL parsing
+  def test_url_parsing(self):
+   with self.assertRaises(tuf.exceptions.URLParsingError) as cm:
+     for chunk in self.fetcher.fetch(self.random_string(), self.file_length):
+         self.temp_file.write(chunk)
+
+
+
+# Run unit test.
+if __name__ == '__main__':
+  utils.configure_test_logging(sys.argv)
+  unittest.main()