docs(upgrade): Adds more detail to upgrade guide.

packages/documentation-site/package.json

@@ -17,7 +17,7 @@
     "screenshots": "pf-docs-framework screenshots"
   },
   "dependencies": {
-    "@patternfly/documentation-framework": "6.0.0-alpha.117",
+    "@patternfly/documentation-framework": "6.0.0-alpha.118",
     "@patternfly/react-catalog-view-extension": "6.0.0-prerelease.1",
     "@patternfly/react-console": "6.0.0-prerelease.2",
     "@patternfly/react-docs": "7.0.0-prerelease.32",

packages/documentation-site/patternfly-docs/content/get-started/upgrade.md

@@ -78,4 +78,22 @@ This codemod works both for CSS variables and React tokens. For example:
 - A CSS variable: `--pf-v5-global--FontSize--lg` becomes `--pf-t--global--font--size--lg`
 - A react token: `global_FontSize_lg` becomes `t_global_font_size_lg`
 
+### 3. Update any pixel-based logic
+
+In PatternFly 6, [we've transitioned from using pixels to using rem units,](/get-started/release-highlights#rem-units) which are relative units that adjust font size based on the HTML document root element size. The root size in PatternFly is 16px, meaning 16px would be 1rem, 24px would be 1.5rems, and so on. 
+
+If you have previously implemented any logic based on a pixel value, you will need to account for the fact that PatternFly 6 size and dimension tokens use rems. Dividing pixel values by 16 will give you the equivalent rem value to use.
+
+### Potential test failures
+
+There are a few test failures that you're likely to encounter: 
+
+1. **Button:** Cannot find `aria-disabled`
+    - We changed button's `isDisabled` prop to assign a value for `disabled`, but none for `aria-disabled`. As a result, any test that looks for `aria-disabled` may fail.
+1. **Button:** Cannot find `disabled` when using `byText`
+    - There's a new wrapping `div` around text in buttons. The RTL `byText` query returns that wrapper instead of the button element itself, which is where button's attributes live. Instead of `byText`, use `byRole` and pass the button text to `name`. This will return the top-level button element.
+1. **Select (when using Jest):** Cannot find `role`
+    - You may get an "unable to find role" error if the Popper menu is set to `aria-disabled` after a selection is made, because the RTL query can't find the menu options. This error only seems to occur with Jest, rather than within the browser. To resolve this, either: 
+        - Pass in the `{hidden: true}` option. 
+        - Change select's `appendTo` to `inline`.