Improve failure messages

[mahendrakariya]

Currently we get AssertionFailure message if a test fails. The message doesn't give details about the expected and actual values. This is particularly the case if the values being compared are collections.

[Dev note]:
We can look at fest-assert for doing assertions. It gives far better error messages. Even the assertion code is more readable.

[sriv]

Closing as stale. Please comment/reopen if this is still valid.