The easiest way to run the TensorFlow unit tests is using Bazel, assuming you have downloaded the source from Git:
# All tests (for C++ changes).
$ bazel test //tensorflow/...
# All Python tests (for Python front-end changes).
$ bazel test //tensorflow/python/...
# All tests (with GPU support).
$ bazel test -c opt --config=cuda //tensorflow/...
$ bazel test -c opt --config=cuda //tensorflow/python/...