test(aliby): ImageDummy.pad_array() method

EVIDENCE THAT COMMIT WORKS:
- issue #53

REFERENCES:

src/aliby/io/image.py

@@ -164,10 +164,6 @@ class ImageDummy(BaseLocalImage):
             extended_array = pad_array(my_da_array, dim = 2, n_empty_slices = 4)
         The additional 4 slices will be filled with zeros.
         """
-        # (If done correctly, these should be true)
-        # tmp[n_empty_slices] == image_array
-        # result.shape[dim] == i+1
-
         # Concats zero arrays with same dimensions as image_array, and puts
         # image_array as last element in list of arrays to be concatenated
         return da.concatenate(

tests/aliby/pipeline/test_image.py

+#!/usr/bin/env python3
+import numpy as np
+import dask.array as da
+import pytest
+
+from aliby.io.image import ImageDummy
+
+tiler_parameters = {"tile_size": 117, "ref_channel": "Brightfield", "ref_z": 0}
+
+sample_da = da.from_array(np.array([[1, 2], [3, 4]]))
+# Make it 5-dimensional
+sample_da = da.reshape(
+    sample_da, (1, 1, sample_da.shape[-2], sample_da.shape[-1])
+)
+
+
+@pytest.mark.parametrize("sample_da", sample_da)
+@pytest.mark.parametrize("dim", 2)
+@pytest.mark.parametrize("n_empty_slices", 4)
+def test_pad_array(sample_da, dim, n_empty_slices):
+    """Test ImageDummy.pad_array() method"""
+    # create object
+    imgdmy = ImageDummy(tiler_parameters)
+    # pads array
+    padded_da = imgdmy.pad_array(
+        sample_da, dim=dim, n_empty_slices=n_empty_slices
+    )
+
+    # select which dimension to index the multidimensional array
+    indices = {dim: n_empty_slices}
+    ix = [
+        indices.get(dim, slice(None))
+        for dim in range(padded_da.compute().ndim)
+    ]
+
+    # Checks that original image array is there and is at the last index
+    assert padded_da.compute(ix) == sample_da
+    # Checks that the additional axis is extended correctly
+    assert padded_da.compute.shape[dim] == n_empty_slices + 1