We have customized a few existing tools to suit our testing and production. Maybe they will also be useful for you as well.
Our latest & greatest online font tester.

Get recipes for inspiration for Indic type sketching.
(Based on the original Type Cooker)

http://motaitalic.com/tools/typecooker/index.html
Our list of books, websites, & tools helpful for Devanagari type design.

http://motaitalic.com/info/type-design-resources/devanagari-type-resources
Some of our previous font testers: Vintage, web-based font testers to proof your fonts: Latin, Devanagari, Hebrew (Beta)
Lists of words useful for testing type: Random & fun, these collections of words were some of the first used to evaluate your type.
Glyphs: It’s our font software of choice. They have a huge library of tutorials and an active forum to help and answer any questions!
Kern-On: A sweet new kerning helper plugin for Glyphs
RMX Tools: Invaluable plugins for Glyphs that help scale and fine-tune your characters. I’ve saved weeks of work thanks to these plugins!
Font Gauntlet: A great type tester for variable fonts that does some wild things!
Wakamaifondue: Website to test out your variable fonts.
Mass-Drive Workshop: A few super-handy tools:
Overview (inspect font info) & Waterfall (list of words of the same lengths)
Hyperglot: Made by Rosetta, this tool might just be the definitive source for checking for language support of your fonts.
Alphabet’s Tools: Alphabet (the company) offers several tools especially useful in helping to define character sets and test for language support.
JAF Text Generator: Simple but handy website to generate sample text to proof fonts
Type Drawers: Not a tool, but an active forum of discussions about anything type-related.