add tests for SBU dataset (#3464)

Co-authored-by: Vasilis Vryniotis <datumbox@users.noreply.github.com>

test/test_datasets.py

@@ -1122,5 +1122,38 @@ class OmniglotTestCase(datasets_utils.ImageDatasetTestCase):
         return num_images_total
 
 
+class SBUTestCase(datasets_utils.ImageDatasetTestCase):
+    DATASET_CLASS = datasets.SBU
+    FEATURE_TYPES = (PIL.Image.Image, str)
+
+    def inject_fake_data(self, tmpdir, config):
+        num_images = 3
+
+        dataset_folder = pathlib.Path(tmpdir) / "dataset"
+        images = datasets_utils.create_image_folder(tmpdir, "dataset", self._create_file_name, num_images)
+
+        self._create_urls_txt(dataset_folder, images)
+        self._create_captions_txt(dataset_folder, num_images)
+
+        return num_images
+
+    def _create_file_name(self, idx):
+        part1 = datasets_utils.create_random_string(10, string.digits)
+        part2 = datasets_utils.create_random_string(10, string.ascii_lowercase, string.digits[:6])
+        return f"{part1}_{part2}.jpg"
+
+    def _create_urls_txt(self, root, images):
+        with open(root / "SBU_captioned_photo_dataset_urls.txt", "w") as fh:
+            for image in images:
+                fh.write(
+                    f"http://static.flickr.com/{datasets_utils.create_random_string(4, string.digits)}/{image.name}\n"
+                )
+
+    def _create_captions_txt(self, root, num_images):
+        with open(root / "SBU_captioned_photo_dataset_captions.txt", "w") as fh:
+            for _ in range(num_images):
+                fh.write(f"{datasets_utils.create_random_string(10)}\n")
+
+
 if __name__ == "__main__":
     unittest.main()