Test install from PyPI with fast-deps

tests/functional/test_fast_deps.py

@@ -0,0 +1,23 @@
+import json
+
+from pip._vendor.packaging.utils import canonicalize_name
+from pytest import mark
+
+
+def assert_installed(script, names):
+    list_output = json.loads(script.pip('list', '--format=json').stdout)
+    installed = {canonicalize_name(item['name']) for item in list_output}
+    assert installed.issuperset(map(canonicalize_name, names))
+
+
+@mark.network
+@mark.parametrize(('req', 'expected'), (
+    ('Paste==3.4.2', ('Paste', 'six')),
+    ('Paste[flup]==3.4.2', ('Paste', 'six', 'flup')),
+))
+def test_install_from_pypi(req, expected, script):
+    script.pip(
+        'install', '--use-feature=fast-deps',
+        req, allow_stderr_warning=True,
+    )
+    assert_installed(script, expected)