I expect this next test in the series doesn't cover the universe, but it will get you further towards whole Earth applications.
The pseudo-localization applied to your text resources should grow the length of the strings. Depending on your application, I recommend the length is increased by about 50%, at least for short strings. The additional text should also include Asian characters, that is, characters from the Han range of Unicode. Let me explain why.
One aspect of testing is edge cases - testing limits and restrictions to see if they are working and how. This includes minimum, below minimum, maximum, and above maximum lengths. Translation usually grows the length of strings, both in byte count and in display. Fields in the user interface (UI) are often limited in length (byte and display), due to display constraints. Expanded pseudo-localized text will show how the UI could change. And more.
What are you looking for? For starters, you're looking at the layout and aesthetics of the UI with the expanded text. Is text wrapping awkwardly? Is it overlapping other text or screen elements? Is it pushing other objects out of position, skewing the overall layout? Do items line up where they're supposed to? Is the text truncated? Obviously limitations are necessary due to screen size, especially for mobile applications. But translators aren't mind readers - they're probably only seeing text in a resource file or translation tool. The only indication they'll have of a length restriction is the comment that you write next to the string to be translated. Which of course you have done.
Remember that I recommended using Asian text in the pseudo-l10n? This is useful for checking that these characters are legible in the space provided; by legible I mean that the stroke lines are distinct and the tops or bottoms of the character are not cut off. Asian characters are often more intricate and complex, requiring a larger font and additional vertical space to be rendered legibly. However, Asian translations will frequently shrink in width. A pseudo-l10n won't bear that out because it usually adds on to the existing string length. But you could run one that replaces the string with shorter Asian character strings, and see what that does to the UI.