Add genesis tests to increase coverage

[MakisChristou]

This PR addresses this issue, by including test cases that increase the genesis coverage from an initial

builder -> 80%
customnet -> 0%
devnet -> 0%
genesis -> 60%
mainnet -> 0%
testnet -> 70.6%

to

builder -> 90%
customnet -> 75%
devnet -> 75.7%
genesis -> 73.3%
mainnet -> 76.4%
testnet -> 70.6%

The lack of 80% coverage across all files is due to the fact that some parts of the code are unreachable. For example see the below snippet. To my understanding we are setting some global hardcoded values to the state and we have some error checking code. Since the value is constant and valid, the error case is never executed thus showing up as uncovered code.

// setup builtin contracts
if err := state.SetCode(builtin.Authority.Address, builtin.Authority.RuntimeBytecodes()); err != nil {
        return err
}

Let me know if I am missing something or if this is indeed coverable code.

@libotony Regarding the unused function its actually used to increase coverage in TestNewDevnetCustomTimestamp

[codecov-commenter]

Codecov Report

Attention: 23 lines in your changes are missing coverage. Please review.

Comparison is base (dbe9923) 55.09% compared to head (e3da2a7) 56.56%.

Files	Patch %	Lines
genesis/devnet.go	46.51%	15 Missing and 8 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #653      +/-   ##
==========================================
+ Coverage   55.09%   56.56%   +1.46%     
==========================================
  Files         179      179              
  Lines       20665    20708      +43     
==========================================
+ Hits        11386    11713     +327     
+ Misses       8442     8105     -337     
- Partials      837      890      +53     

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[libotony]

@libotony Regarding the unused function its actually used to increase coverage in TestNewDevnetCustomTimestamp

If I remember correctly, the function NewDevnetCustomTimestamp was introduced for txpool tests in #636 and we didn't use it at the end, so I am suggesting remove both NewDevnetCustomTimestamp and TestNewDevnetCustomTimestamp, since TestNewDevnetCustomTimestamp is not used in the code base.

[libotony]

The lack of 80% coverage across all files is due to the fact that some parts of the code are unreachable. For example see the below snippet. To my understanding we are setting some global hardcoded values to the state and we have some error checking code. Since the value is constant and valid, the error case is never executed thus showing up as uncovered code.

// setup builtin contracts
if err := state.SetCode(builtin.Authority.Address, builtin.Authority.RuntimeBytecodes()); err != nil {
        return err
}

I would consider this acceptable, otherwise you might need to make a customized stateDB implementation that always throws error for setCode @nwbrettski we can discuss this during our standups.

[nwbrettski]

I agree @libotony this is acceptable. It is an improvement. We can always take another look to improve further at a later date if required.