test for check-already-downloaded feature

tests/test_download.py

@@ -39,3 +39,31 @@ def test_download_should_download_dependencies():
     openid_tarball_prefix = str(Path('scratch')/ 'python-openid-')
     assert any(path.startswith(openid_tarball_prefix) for path in result.files_created)
     assert env.site_packages/ 'openid' not in result.files_created
+
+
+def test_download_should_skip_existing_files():
+    """
+    It should not download files already existing in the scratch dir
+    """
+    env = reset_env()
+
+    write_file('test-req.txt', textwrap.dedent("""
+        INITools==0.1
+        """))
+
+    result = run_pip('install', '-r', env.scratch_path/ 'test-req.txt', '-d', '.', expect_error=True)
+    assert Path('scratch')/ 'INITools-0.1.tar.gz' in result.files_created
+    assert env.site_packages/ 'initools' not in result.files_created
+
+    # adding second package to test-req.txt
+    write_file('test-req.txt', textwrap.dedent("""
+        INITools==0.1
+        python-openid==2.2.5
+        """))
+
+    # only the second package should be downloaded
+    result = run_pip('install', '-r', env.scratch_path/ 'test-req.txt', '-d', '.', expect_error=True)
+    assert Path('scratch')/ 'python-openid-2.2.5.zip' in result.files_created
+    assert Path('scratch')/ 'INITools-0.1.tar.gz' not in result.files_created
+    assert env.site_packages/ 'initools' not in result.files_created
+    assert env.site_packages/ 'openid' not in result.files_created