update colorbar tests (#40)

* update colorbar tests

* refactor and fix

* changelog

* also test ax=ax

Author: mathause

CHANGELOG.md

@@ -16,7 +16,8 @@
 ### Bug fixes
 
  * Fixed compatibility of `mpu.colorbar` with `bbox_inches="tight"` for matplotlib 3.4 and
-   newer ([#26](https://github.com/mathause/mplotutils/pull/26)).
+   newer and refactor and extend tests ([#26](https://github.com/mathause/mplotutils/pull/26)
+   and [#40](https://github.com/mathause/mplotutils/pull/40)).
 
 ### Internal changes
 

mplotutils/_colorbar.py

@@ -14,7 +14,7 @@ def colorbar(
     pad=None,
     shift="symmetric",
     shrink=None,
-    **kwargs
+    **kwargs,
 ):
     """
     automatically resize colorbars on draw
@@ -389,7 +389,7 @@ def inner(event=None):
             height = size_scaled
         else:
             figure_aspect = np.divide(*f.get_size_inches())
-            height = (width * figure_aspect) / (aspect)
+            height = width * (aspect * figure_aspect)
 
         left = posn1.x0 + shift * full_width
         bottom = posn1.y0 - (pad_scaled + height)