diff --git a/src/tests/README.md b/src/tests/README.md
index 6920626..5037048 100644
--- a/src/tests/README.md
+++ b/src/tests/README.md
@@ -20,6 +20,16 @@ These generate their own data and run without external files.
 | `test_xor.py` | BB-RBM | Auto-encoder on XOR-like 3-bit patterns using the older `Layer` API. |
 | `test_gaussian_autoencoder.py` | GB-RBM | Auto-encoder on synthetic Gaussian blob images (8×8). Trains, reconstructs, and plots original vs. reconstruction. |
 | `test_linear.py` | GB-RBM or GG-RBM | GB/GG-RBM on random continuous data (3000-dim). Toggle `do_gaussian_hidden` at the top of the file. |
+
+---
+
+## Tests requiring external image data
+
+These load images from a fixed path on disk.
+
+| File | RBM type | What it tests |
+|---|---|---|
+| `test_faces_sub_image.py` | GB-RBM | Auto-encoder on 32×32 RGB patches extracted from Caltech WebFaces (`/media/jens/cifs/bilder/MachineVision/Caltech_WebFaces/`). Uses `SubImage` for non-overlapping ROI extraction (stride=32). After training: shows 128 learned weight filters, patch-level reconstructions, and a full image reconstruction assembled from patches. |
 | `test_sub_image.py` | — | Unit test for `SubImage` (patch extraction). No RBM involved. |
 | `test_conv2d.py` | — | Unit test for `conv2d`. No RBM involved. |