[test] Add support for retrieving stdlib events

[m-Peter]

Description

• Fix regex issue, when parsing non-string log messages
• Add support for stdlib events that have type flow.*
• Allow importing the Test contract in helper files
• Update EmulatorBackend.Reset() function to use Blockchain.RollbackToBlockHeight() instead of Blockchain.ReloadBlockchain()
• Improve CoverageReport metrics to include only contracts

Such events, can even be printed to the console:

1:04PM DBG LOG: flow.AccountCreated(address: 0x01cf0e2f2f715450)

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• Targeted PR against master branch
• Linked to Github issue with discussion and accepted design OR link to spec that describes this work
• Code follows the standards mentioned here
• Updated relevant documentation
• Re-reviewed Files changed in the Github PR explorer
• Added appropriate labels

[m-Peter]

@SupunS I have added a simplified version to check the case which you described in #113 (comment). Even though we do create a new Test.Blockchain struct, with every call of Test.newEmulatorBlockchain(), the underlying backend implementation is always the same (per test-file that is, because on flow-cli I do create a new TestRunner for each test-file). What do you think? Are we covered here?

[SupunS]

I have added a simplified version to check the case which you described in #113 (comment). Even though we do create a new Test.Blockchain struct, with every call of Test.newEmulatorBlockchain(), the underlying backend implementation is always the same (per test-file that is, because on flow-cli I do create a new TestRunner for each test-file). What do you think? Are we covered here?

Oh, that looks like a bug in the original implementation. Test.newEmulatorBlockchain() should ideally return a fresh backend instance everytime. We don't have to fix it here, but maybe can you report an issue for this for now?

[m-Peter]

Oh, that looks like a bug in the original implementation. Test.newEmulatorBlockchain() should ideally return a fresh backend instance everytime. We don't have to fix it here, but maybe can you report an issue for this for now?

In fact, the backend instance is created once in the ContractValueHandler, when the Test contract is first encountered in a test file. To me, it makes sense to provide just a Test.Blockchain singleton in every test file. Especially now that Reset() is supported. Instead of Test.newEmulatorBlockchain, just Test.emulatorBlockchain. That's a breaking change for the API though 😇 . What is your opinion on this? What's the best approach to solve this? I am asking so I can put it in an issue.

[SupunS]

That is certainly an alternative solution. But then again, if the emulatorBlockchain is a singleton, we would not even need to expose it. i.e. instead of Test.emulatorBlockchain.executeScript() we can do Test.executeScript() because anyway only one blockchain is used.

We can open the issue just by mentioning the current problem (i.e: newEmulatorBlockchain returns the same instance) and then discuss the details/different solutions in the issue itself.
I can open the issue if you want me to :)

[m-Peter]

@SupunS #139 🙌

[m-Peter]

I have complemented the test suite with some tests for the Blockchain.reset method, and I had to change its implementation to get the desired functionality. I think this should be all for this PR 🙏
cc @SupunS @turbolent

[turbolent]

Nice!