Remove chai-as-promised

[justuswilhelm]

Addresses #1091 -- it's about @nventuro's comment about removing chai-as-promised

🚀 Description

I'm doing a few things here:

1. I enhanced expectThrow to test for one particular EVM message, e.g. invalid opcode
2. I change all test cases to either just await and be done, or I use expectThrow and test for a specific exception message
3. I remove chai-as-promised from package.json

• 📘 I've reviewed the OpenZeppelin Contributor Guidelines
• ✅ I've added tests where applicable to test my new functionality.
• 📖 I've made sure that my contracts are well-documented.
• 🎨 I've run the JS/Solidity linters and fixed any issues (npm run lint:all:fix).

[nventuro]

This is awesome, thank you very much @justuswilhelm!

If you're into testing, there's a couple more easy issues that need love: two bugfixes (#775 and #938) and two features (#917 and #942). We plan on exporting our testing helpers soon for users of the library (#326), so these will be super helpful.

Thanks again!

[nventuro]

Could you change this brace for an else, to emphasize the fact that the message parameter changes the usual behavior?

[justuswilhelm]

Yes, absolutely. Let me fix that.

[justuswilhelm]

Thanks for pointing out some other issues I can work on, @nventuro . And yes, I do enjoy working on test code! 👍

[nventuro]

Great, thanks!

By the way, we do squash merges, so there's no need to rebase your branch when addressing reviews. Not doing that actually makes our job easier, since we can easily see what changed from review to review :)

[justuswilhelm]

@nventuro Much appreciated! Re. the squashing, noted!