Add tests for ngclient/fetcher

Add tests for the file/data download.

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

tests/test_fetcher_ng.py

@@ -0,0 +1,150 @@
+#!/usr/bin/env python
+
+# Copyright 2021, New York University and the TUF contributors
+# SPDX-License-Identifier: MIT OR Apache-2.0
+
+"""Unit test for RequestsFetcher.
+"""
+
+import io
+import logging
+import os
+import sys
+import unittest
+import tempfile
+import math
+
+from tests import utils
+from tuf import exceptions, unittest_toolbox
+from tuf.ngclient._internal.requests_fetcher import RequestsFetcher
+
+logger = logging.getLogger(__name__)
+
+
+class TestFetcher(unittest_toolbox.Modified_TestCase):
+
+    @classmethod
+    def setUpClass(cls):
+        # Launch a SimpleHTTPServer (serves files in the current dir).
+        cls.server_process_handler = utils.TestServerProcess(log=logger)
+
+    @classmethod
+    def tearDownClass(cls):
+        # Stop server process and perform clean up.
+        cls.server_process_handler.clean()
+
+    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 data 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)
+        self.rel_target_filepath = os.path.basename(target_filepath)
+        self.url = f"http://{utils.TEST_HOST_ADDRESS}:{str(self.server_process_handler.port)}/{self.rel_target_filepath}"
+
+        # Instantiate a concrete instance of FetcherInterface
+        self.fetcher = RequestsFetcher()
+
+    def tearDown(self):
+        self.target_fileobj.close()
+        # Remove temporary directory
+        unittest_toolbox.Modified_TestCase.tearDown(self)
+
+    # Simple fetch.
+    def test_fetch(self):
+        with tempfile.TemporaryFile() as temp_file:
+            for chunk in self.fetcher.fetch(self.url):
+                temp_file.write(chunk)
+
+            temp_file.seek(0)
+            self.assertEqual(
+                self.file_contents, temp_file.read().decode("utf-8")
+            )
+
+    # URL data downloaded in more than one chunk
+    def test_fetch_in_chunks(self):
+        # Set a smaller chunk size to ensure that the file will be downloaded
+        # in more than one chunk
+        self.fetcher.chunk_size = 4
+
+        # expected_chunks_count: 3
+        expected_chunks_count = math.ceil(
+            self.file_length / self.fetcher.chunk_size
+        )
+        self.assertEqual(expected_chunks_count, 3)
+
+        chunks_count = 0
+        with tempfile.TemporaryFile() as temp_file:
+            for chunk in self.fetcher.fetch(self.url):
+                temp_file.write(chunk)
+                chunks_count += 1
+
+            temp_file.seek(0)
+            self.assertEqual(
+                self.file_contents, temp_file.read().decode("utf-8")
+            )
+            # Check that we calculate chunks as expected
+            self.assertEqual(chunks_count, expected_chunks_count)
+
+    # Incorrect URL parsing
+    def test_url_parsing(self):
+        with self.assertRaises(exceptions.URLParsingError):
+            self.fetcher.fetch(self.random_string())
+
+    # File not found error
+    def test_http_error(self):
+        with self.assertRaises(exceptions.FetcherHTTPError) as cm:
+            self.url = f"http://{utils.TEST_HOST_ADDRESS}:{str(self.server_process_handler.port)}/non-existing-path"
+            self.fetcher.fetch(self.url)
+        self.assertEqual(cm.exception.status_code, 404)
+
+    # Simple bytes download
+    def test_download_bytes(self):
+        data = self.fetcher.download_bytes(self.url, self.file_length)
+        self.assertEqual(self.file_contents, data.decode("utf-8"))
+
+    # Download file smaller than required max_length
+    def test_download_bytes_upper_length(self):
+        data = self.fetcher.download_bytes(self.url, self.file_length + 4)
+        self.assertEqual(self.file_contents, data.decode("utf-8"))
+
+    # Download a file bigger than expected
+    def test_download_bytes_length_mismatch(self):
+        with self.assertRaises(exceptions.DownloadLengthMismatchError):
+            self.fetcher.download_bytes(self.url, self.file_length - 4)
+
+    # Simple file download
+    def test_download_file(self):
+        with self.fetcher.download_file(
+            self.url, self.file_length
+        ) as temp_file:
+            temp_file.seek(0, io.SEEK_END)
+            self.assertEqual(self.file_length, temp_file.tell())
+
+    # Download file smaller than required max_length
+    def test_download_file_upper_length(self):
+        with self.fetcher.download_file(
+            self.url, self.file_length + 4
+        ) as temp_file:
+            temp_file.seek(0, io.SEEK_END)
+            self.assertEqual(self.file_length, temp_file.tell())
+
+    # Download a file bigger than expected
+    def test_download_file_length_mismatch(self):
+        with self.assertRaises(exceptions.DownloadLengthMismatchError):
+            yield self.fetcher.download_file(self.url, self.file_length - 4)
+
+
+# Run unit test.
+if __name__ == "__main__":
+    utils.configure_test_logging(sys.argv)
+    unittest.main()