Add some tests about block_size argument

Author: munshkr

README.md

@@ -50,6 +50,16 @@ dask.array<and_, shape=(3, 718, 791), dtype=uint8, chunksize=(1, 3, 791)>
 >>> write_raster('processed_image.tif', new_array, **prof)
 ```
 
+#### Chunk size
+
+Both `read_raster` and `write_raster` accept a `block_size` argument that
+acts as a multiplier to the block size of rasters. The default value is 1,
+which means the dask array chunk size will be the same as the block size of
+the raster file. You will have to adjust this value depending on the
+specification of your machine (how much memory do you have, and the block
+size of the raster).
+
+
 ## Install
 
 Install with pip:

tests/test_dask_rasterio.py

@@ -183,3 +183,25 @@ def test_cannot_write_raster_with_badly_shaped_array(some_raster_path):
 
         with pytest.raises(TypeError):
             write_raster(dst_path, np.random.rand(10, 10, 10, 3), **prof)
+
+
+def multiply_chunks(chunks, multiplier):
+    w_chunks = tuple(np.array([list(chunks[0])])) * multiplier
+    h_chunks = tuple(np.array([list(chunks[1])])) * multiplier
+    return (w_chunks, h_chunks)
+
+
+def test_read_raster_band_with_block_size(some_raster_path):
+    array = read_raster_band(some_raster_path)
+    array_4b = read_raster_band(some_raster_path, block_size=4)
+    assert array.shape == array_4b.shape
+    assert array.dtype == array_4b.dtype
+    assert_array_equal(array, array_4b)
+
+    with rasterio.open(some_raster_path) as src:
+        ch, cw = src.block_shapes[0]
+
+    assert array.chunks[0][0] == ch
+    assert array.chunks[1][0] == cw
+    assert array_4b.chunks[0][0] == ch * 4
+    assert array_4b.chunks[1][0] == cw * 4