Adds support for EXAMPLE_DIR config to tfds tests.

PiperOrigin-RevId: 238093283

Author: dbieber

tensorflow_datasets/testing/dataset_builder_testing.py

@@ -77,6 +77,9 @@ class DatasetBuilderTestCase(parameterized.TestCase, test_utils.SubTestCase):
       `download_and_extract` method. The values should be the path of files
       present in the `fake_examples` directory, relative to that directory.
       If not specified, path to `fake_examples` will always be returned.
+    EXAMPLE_DIR: `str`, the base directory in in which fake examples are
+      contained. Optional; defaults to
+      tensorflow_datasets/testing/test_data/fake_examples/<dataset name>.
     OVERLAPPING_SPLITS: `list[str]`, splits containing examples from other
       splits (e.g. a "example" split containing pictures from other splits).
     MOCK_OUT_FORBIDDEN_OS_FUNCTIONS: `bool`, defaults to True. Set to False to
@@ -100,6 +103,7 @@ class DatasetBuilderTestCase(parameterized.TestCase, test_utils.SubTestCase):
   DATASET_CLASS = None
   BUILDER_CONFIG_NAMES_TO_TEST = []
   DL_EXTRACT_RESULT = None
+  EXAMPLE_DIR = None
   OVERLAPPING_SPLITS = []
   MOCK_OUT_FORBIDDEN_OS_FUNCTIONS = True
 
@@ -117,9 +121,14 @@ def setUp(self):
     super(DatasetBuilderTestCase, self).setUp()
     self.patchers = []
     self.builder = self._make_builder()
+
+    # Determine the fake_examples directory.
     self.example_dir = os.path.join(
         os.path.dirname(__file__),
         "test_data/fake_examples/%s" % self.builder.name)
+    if self.EXAMPLE_DIR is not None:
+      self.example_dir = self.EXAMPLE_DIR
+
     if not tf.io.gfile.exists(self.example_dir):
       err_msg = "fake_examples dir %s not found." % self.example_dir
       raise ValueError(err_msg)