Feedback of contract-coverager

[syuhei176]

Hello! This is my feedback.

I have 2 small problems.

First, now plasma-predicate has 2 test. When I remove CoverageSubprovider from one test, npm test hangs. When I add CoverageSubprovider to both tests, tests are passed.

Second, when I ran the test of our OwnershipPredicate.test.js, the test was passed but errors happen. Descriptions are below. I'm not sure this depends on the contract-coverager or not. But when I remove lines using contract-coverager, the error didn't happen.

This is source code.
https://github.com/cryptoeconomicslab/plasma-predicates/pull/11

  Contract: OwnershipPredicate
    canStartExitGame
      ✓ succeed to canStartExitGame (177ms)
    executeStateTransition
Error: the tx doesn't have the correct nonce. account has nonce of: 1 tx has nonce of: 0
    at Object._fireError (/Users/syuhei/work/cel/plasma-predicates/node_modules/truffle/build/webpack:/~/web3-utils/src/index.js:56:1)
    at sendTxCallback (/Users/syuhei/work/cel/plasma-predicates/node_modules/truffle/build/webpack:/~/web3-eth/~/web3-core-method/src/index.js:491:1)
    at /Users/syuhei/work/cel/plasma-predicates/node_modules/truffle/build/webpack:/~/web3-eth/~/web3-core-requestmanager/src/index.js:136:1
    at /Users/syuhei/work/cel/plasma-predicates/node_modules/web3-provider-engine/index.js:190:9
    at /Users/syuhei/work/cel/plasma-predicates/node_modules/async/internal/once.js:12:16
    at replenish (/Users/syuhei/work/cel/plasma-predicates/node_modules/async/internal/eachOfLimit.js:61:25)
    at /Users/syuhei/work/cel/plasma-predicates/node_modules/async/internal/eachOfLimit.js:71:9
    at eachLimit (/Users/syuhei/work/cel/plasma-predicates/node_modules/async/eachLimit.js:43:36)
    at /Users/syuhei/work/cel/plasma-predicates/node_modules/async/internal/doLimit.js:9:16
    at end (/Users/syuhei/work/cel/plasma-predicates/node_modules/web3-provider-engine/index.js:169:5)
    at traceFunc.then.res (/Users/syuhei/work/cel/plasma-predicates/node_modules/contract-coverager/src/coverage_subprovider.js:191:34)
    at process._tickCallback (internal/process/next_tick.js:68:7)
0xf86cb840000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000027109413274fe19c0178208bcbee397af8167a7be27f6f94f17f52151ebef6c7334fad080c5704d77216b732
      ✓ succeed to executeStateTransition (599ms)

Thank you!