[tests] relocate core integration tests (#11146)

* relocate core integration tests

* add sys.path context manager

* cleanup

* try

* try2

* fix path

* doc

* style

* add dep

* add 2 more deps

docs/source/main_classes/trainer.rst

@@ -525,7 +525,7 @@ Here is an example of running ``run_translation.py`` under DeepSpeed deploying a
 .. code-block:: bash
 
     deepspeed examples/seq2seq/run_translation.py \
-    --deepspeed examples/tests/deepspeed/ds_config.json \
+    --deepspeed tests/deepspeed/ds_config.json \
     --model_name_or_path t5-small --per_device_train_batch_size 1   \
     --output_dir output_dir --overwrite_output_dir --fp16 \
     --do_train --max_train_samples 500 --num_train_epochs 1 \
@@ -550,7 +550,7 @@ To deploy DeepSpeed with one GPU adjust the :class:`~transformers.Trainer` comma
 .. code-block:: bash
 
     deepspeed --num_gpus=1 examples/seq2seq/run_translation.py \
-    --deepspeed examples/tests/deepspeed/ds_config.json \
+    --deepspeed tests/deepspeed/ds_config.json \
     --model_name_or_path t5-small --per_device_train_batch_size 1   \
     --output_dir output_dir --overwrite_output_dir --fp16 \
     --do_train --max_train_samples 500 --num_train_epochs 1 \

docs/source/testing.rst

@@ -1,4 +1,4 @@
-.. 
+..
     Copyright 2020 The HuggingFace Team. All rights reserved.
 
     Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
@@ -388,7 +388,7 @@ For a single or a group of tests via ``pytest`` (after ``pip install pytest-pspe
 
 .. code-block:: bash
 
-   pytest --pspec tests/test_optimization.py 
+   pytest --pspec tests/test_optimization.py
 
 
 
@@ -672,7 +672,7 @@ and it will list:
 
     test_this2.py::test_floor[integer-1-1.0]
     test_this2.py::test_floor[negative--1.5--2.0]
-    test_this2.py::test_floor[large fraction-1.6-1]       
+    test_this2.py::test_floor[large fraction-1.6-1]
 
 So now you can run just the specific test:
 
@@ -795,6 +795,23 @@ leave any data in there.
    otherwise.
 
 
+Temporary sys.path override
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+If you need to temporary override ``sys.path`` to import from another test for example, you can use the
+``ExtendSysPath`` context manager. Example:
+
+
+.. code-block:: python
+
+    import os
+    from transformers.testing_utils import ExtendSysPath
+    bindir = os.path.abspath(os.path.dirname(__file__))
+    with ExtendSysPath(f"{bindir}/.."):
+        from test_trainer import TrainerIntegrationCommon  # noqa
+
+
+
 Skipping tests
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~