Updated testing part of the documentation:

doc/install.txt

@@ -243,30 +243,21 @@ You can also run them in-place from the Mercurial checkout directory by typing
 
     nosetests
 
-``THEANO_FLAGS`` is an environment variable that define Theano flags
-(:ref:`libdoc_config`).  For Windows users, you can remove it or see the
-documentation to know how to configure them differently.
-
 .. note::
 
-    The tests should be run with the ``THEANO_FLAGS`` ``device=cpu`` (default).
-    Otherwise, it will generate false errors. If you have a GPU, it will
-    automatically be used to run GPU-related tests.
+    The tests should be run with the :attr:`~config.device` option set to
+    ``cpu``, e.g. with prefixing the ``nosetests`` command with
+    ``THEANO_FLAGS=device=cpu``. If you have a GPU, it will automatically
+    be used to run GPU-related tests.
 
-    If you want the GPU-related tests to run on a specific GPU device, and not
+    If you want GPU-related tests to run on a specific GPU device, and not
     the default one, you should use :attr:`~config.init_gpu_device`, for
-    instance ``THEANO_FLAGS=init_gpu_device=gpu1``.
+    instance ``THEANO_FLAGS=device=cpu,init_gpu_device=gpu1``.
 
 All tests should pass except those marked as ``KnownFailureTest``. If some
 test fails on your machine, you are encouraged to tell us what went wrong on
 the ``theano-users@googlegroups.com`` mailing list.
 
-.. note::
-
-    ``warn.ignore_bug_before=all`` removes warnings that you don't need to see
-    here.  It is also recommended for a new user to set this flag to a
-    different value in their ``.theanorc`` file.  See
-    :attr:`.config.warn.ignore_bug_before` for more details.
 
 Troubleshooting: Make sure you have a BLAS library
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~