Add a guide on how to use TestPyPI (pypa#366)

Author: Jon Wayne Parrott

source/guides/index.rst

@@ -21,3 +21,4 @@ introduction to packaging, see :doc:`/tutorials/index`.
    index-mirrors-and-caches
    hosting-your-own-index
    migrating-to-pypi-org
+   using-testpypi

source/guides/using-testpypi.rst

@@ -0,0 +1,78 @@
+==============
+Using TestPyPI
+==============
+
+`TestPyPI` is a separate instance of the :term:`Python Package Index (PyPI)`
+that allows you to try out the distribution tools and process without worrying
+about affecting the real index. TestPyPI is hosted at
+`test.pypi.org <https://test.pypi.org>`_
+
+Registering your account
+------------------------
+
+Because TestPyPI has a separate database from the live PyPI, you'll need a
+separate user account for specifically for TestPyPI. Go to
+https://test.pypi.org/account/register/ to register your account.
+
+.. Note:: The database for TestPyPI may be periodically pruned, so it is not
+    unusual for user accounts to be deleted.
+
+
+Using TestPyPI with Twine
+-------------------------
+
+You can upload your distributions to TestPyPI using :ref:`twine` by passing
+in the ``--repository-url`` flag
+
+.. code::
+
+    $ twine upload --repository-url https://test.pypi.org/legacy/ dist/*
+
+Using TestPyPI with pip
+-----------------------
+
+You can tell pip to download packages from TestPyPI instead of PyPI by
+specifying the ``--index-url`` flag
+
+.. code::
+
+    $ pip install --index-url https://test.pypi.org/simple/ your-package
+
+If you want to allow pip to also pull other packages from PyPI you can
+specify ``--extra-index-url`` to point to PyPI. This useful when the package
+you're testing has dependencies:
+
+.. code::
+
+    pip install --index-url https://test.pypi.org/simple/ --extra-index-url https://pypi.org/simple your-package
+
+Setting up TestPyPI in pypirc
+-----------------------------
+
+If you want to avoid entering the TestPyPI url and your username and password
+you can configure TestPyPI in your ``~/.pypirc``.
+
+Create or modify ``~/.pypirc`` with the following:
+
+.. code::
+
+    [distutils]
+    index-servers=
+        pypi
+        testpypi
+
+    [testpypi]
+    repository: https://test.pypi.org/legacy/
+    username: your testpypi username
+    password: your testpypi password
+
+
+.. Warning:: This stores your password in plaintext. It's recommended to set
+    narrow permissions on this file.
+
+You can then tell :ref:`twine` to upload to TestPyPI by specifying the
+``--repository`` flag:
+
+.. code::
+
+    $ twine upload --repository testpypi dist/*