diff --git a/sparsecoding/datasets.py b/sparsecoding/datasets.py
index 13c82a8..c2b58cf 100644
--- a/sparsecoding/datasets.py
+++ b/sparsecoding/datasets.py
@@ -1,7 +1,7 @@
 import torch
 import os
 from scipy.io import loadmat
-from sparsecoding.transforms import patchify
+from sparsecoding.transforms import sample_random_patches
 from torch.utils.data import Dataset
 
 from sparsecoding.priors import Prior
@@ -79,10 +79,11 @@ class FieldDataset(Dataset):
     root : str
         Location to download the dataset to.
     patch_size : int
-        Side length of patches for sparse dictionary learning.
-    stride : int, optional
-        Stride for sampling patches. If not specified, set to `patch_size`
-        (non-overlapping patches).
+        Side length of patches to extract from images.
+    num_patches : int
+        Number of patches to extract from images.
+    whitened : bool, default=True
+        Download the whitened or unwhitened dataset.
     """
 
     B = 10
@@ -93,27 +94,31 @@ class FieldDataset(Dataset):
     def __init__(
         self,
         root: str,
+        num_patches: int,
         patch_size: int = 8,
-        stride: int = None,
+        whitened: bool = True
     ):
         self.P = patch_size
-        if stride is None:
-            stride = patch_size
 
         root = os.path.expanduser(root)
         os.system(f"mkdir -p {root}")
-        if not os.path.exists(f"{root}/field.mat"):
-            os.system("wget https://rctn.org/bruno/sparsenet/IMAGES.mat")
-            os.system(f"mv IMAGES.mat {root}/field.mat")
-
-        self.images = torch.tensor(loadmat(f"{root}/field.mat")["IMAGES"])  # [H, W, B]
+        if whitened:
+            filename = "IMAGES.mat"
+            key = "IMAGES"
+        else:
+            filename = "IMAGES_RAW.mat"
+            key = "IMAGESr"
+        path_to_dataset = os.path.join(root, filename)
+        if not os.path.exists(path_to_dataset):
+            os.system(f"wget https://rctn.org/bruno/sparsenet/{filename} -P {root}")
+
+        self.images = torch.from_numpy(loadmat(path_to_dataset)[key].astype(float))  # [H, W, B]
         assert self.images.shape == (self.H, self.W, self.B)
 
         self.images = torch.permute(self.images, (2, 0, 1))  # [B, H, W]
         self.images = torch.reshape(self.images, (self.B, self.C, self.H, self.W))  # [B, C, H, W]
 
-        self.patches = patchify(patch_size, self.images, stride)  # [B, N, C, P, P]
-        self.patches = torch.reshape(self.patches, (-1, self.C, self.P, self.P))  # [B*N, C, P, P]
+        self.patches = sample_random_patches(patch_size, num_patches, self.images)  # [N, C, P, P]
 
     def __len__(self):
         return self.patches.shape[0]
diff --git a/sparsecoding/test_datasets.py b/sparsecoding/test_datasets.py
new file mode 100644
index 0000000..a38f231
--- /dev/null
+++ b/sparsecoding/test_datasets.py
@@ -0,0 +1,18 @@
+import pytest
+from sparsecoding.datasets import FieldDataset
+
+
+@pytest.mark.parametrize("whitened", [True, False])
+def test_FieldDataset(
+        patch_size_fixture: int,
+        dataset_size_fixture: int,
+        whitened: bool,
+):
+    fielddataset = FieldDataset(
+        root="data",
+        num_patches=dataset_size_fixture,
+        patch_size=patch_size_fixture,
+        whitened=whitened
+    )
+    assert len(fielddataset) == dataset_size_fixture
+    assert fielddataset.patches.shape == (dataset_size_fixture, 1, patch_size_fixture, patch_size_fixture)
diff --git a/sparsecoding/transforms/images.py b/sparsecoding/transforms/images.py
index cd48994..fb86e1e 100644
--- a/sparsecoding/transforms/images.py
+++ b/sparsecoding/transforms/images.py
@@ -33,7 +33,7 @@ def check_images(images: torch.Tensor, algorithm: str = "zca"):
         )
 
 
-def whiten_images(images: torch.Tensor, algorithm: str, stats: Dict = None, **kwargs) -> torch.Tensor:
+def whiten_images(images: torch.Tensor, algorithm: str, stats: Optional[Dict] = None, **kwargs) -> torch.Tensor:
     """
     Wrapper for all whitening transformations
 
@@ -335,7 +335,7 @@ def sample_random_patches(
 def patchify(
     patch_size: int,
     image: torch.Tensor,
-    stride: int = None,
+    stride: Optional[int] = None,
 ):
     """Break an image into square patches.
 
diff --git a/sparsecoding/transforms/whiten.py b/sparsecoding/transforms/whiten.py
index c2ad175..8028fce 100644
--- a/sparsecoding/transforms/whiten.py
+++ b/sparsecoding/transforms/whiten.py
@@ -1,5 +1,5 @@
 import torch
-from typing import Dict
+from typing import Dict, Optional
 
 
 def compute_whitening_stats(X: torch.Tensor):
@@ -33,8 +33,8 @@ def compute_whitening_stats(X: torch.Tensor):
 def whiten(
     X: torch.Tensor,
     algorithm: str = "zca",
-    stats: Dict = None,
-    n_components: float = None,
+    stats: Optional[Dict] = None,
+    n_components: Optional[float] = None,
     epsilon: float = 0.0,
     return_W: bool = False,
 ) -> torch.Tensor: