adding more explanation to the tests

.codecov.yml

@@ -0,0 +1,18 @@
+coverage:
+  range: 50..90
+  round: down
+  precision: 2
+  status:
+    project:
+      # full project
+      default:
+        target: 90%
+        threshold: 5%
+        base: auto
+    patch:
+      # just the lines changed
+      default:
+        target: 50%
+        threshold: 10%
+        base: auto
+        only_pulls: false

astrocut/tests/test_cutout_processing.py

@@ -259,6 +259,14 @@ def test_center_on_path(tmpdir):
 
 
 def test_default_combine():
+    """
+    The build_default_combine_function function uses the input hdus
+    to determine which pixels will be used by the combiner function
+    when combining images. The returned combiner function applies
+    that mask before taking the mean of all non-masked pixels to get the
+    output image.
+    """
+
     hdu_1 = fits.ImageHDU(np.array([[1, 1], [0, 0]]))
     hdu_2 = fits.ImageHDU(np.array([[0, 0], [1, 1]]))