Reduce boilerplate in test code

[turadg]

What is the Problem Being Solved?

Tests duplicate a lot of setup. (E.g. creating a brand object) This creates extra work to write and even more to refactor.

Description of the Design

Extract repeated patterns into test util modules. Make some Ava macros for common assertions.

Security Considerations

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Test Plan

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[Tartuffo]

@dtribble Please add your thoughts.

[dtribble]

Example:

• ava support for comparing amounts with e.g., t.deepEqual
• better support for launching the contract instances needed by a test
• shared setup for zoe
• shared setup for remoting boundary to contracts
• shared initial values (including helpers for basis points, amount tracking, etc.)
• shared helpers for governance