Notes

1. Utils is not a static library because we want to mock it, which means it needs to be aligned with our dependency injection framework.
   • mocking it in the hub test to generate fake state updates that pass validation
2. Validate exchange BN division and rounding between Hub and Client
3. ExchangeArgumentsBN -> ExchangeArgsBN

Testing

There are a number of helper functions to make testing easier::

   import { assert, getChannelState, updateState, assertStateEqual } from 'client/testing'

   describe('confirm deposit', () => {
      const preDepositState = getChannelState('empty', {
         balanceWei: [0, 0],
         pendingDepositWei: [6, 9],
      })

      it('should add the correct amount', () => {
         let actual = confirmDeposit(preDepositState)
         assertStateEqual(actual, {
            balanceWei: [6, 9],
            pendingDepositWei: [0, 0],
         })
      })
   })

Notice that:

1. The testing library provides four "default" states: "empty" (where all fields are zero, except for the txCount, which is [1, 1] or 1 for channels and threads, respectively), and "full", where each field has a unique value (this is useful for testing, ex, signature functions).

   "empty" channel state::

      contractAddress: '0xCCC0000000000000000000000000000000000000'
      user: '0xAAA0000000000000000000000000000000000000'
      recipient: '0x2220000000000000000000000000000000000000'
      balanceWei: [ '0', '0' ]
      balanceToken: [ '0', '0' ]
      pendingDepositWei: [ '0', '0' ]
      pendingDepositToken: [ '0', '0' ]
      pendingWithdrawalWei: [ '0', '0' ]
      pendingWithdrawalToken: [ '0', '0' ]
      txCount: [ 1, 1 ],
      threadRoot: '0x0000000000000000000000000000000000000000000000000000000000000000'
      threadCount: 0
      timeout: 0
      sig: [ '', '' ]

"full" channel state::

      contractAddress: '0xCCC0000000000000000000000000000000000000'
      user: '0xAAA0000000000000000000000000000000000000'
      recipient: '0x2220000000000000000000000000000000000000'
      balanceWei: [ '1', '2' ]
      balanceToken: [ '3', '4' ]
      pendingDepositWei: [ '4', '5' ]
      pendingDepositToken: [ '6', '7' ]
      pendingWithdrawalWei: [ '8', '9' ]
      pendingWithdrawalToken: [ '10', '11' ]
      txCount: [ 13, 12 ]
      threadRoot: '0x1414140000000000000000000000000000000000000000000000000000000000'
      threadCount: 14
      timeout: 15
      sig: [ 'sighub0000000000000000000000000000000000000000000000000000000000', 'siguser0000000000000000000000000000000000000000000000000000000000' ] 

"empty" thread state::

      contractAddress: '0xCCC0000000000000000000000000000000000000'
      user: '0xAAA0000000000000000000000000000000000000'
      sender: '0x2220000000000000000000000000000000000000'
      receiver: '0x3330000000000000000000000000000000000000'
      txCount: 1
      balanceWei: [ '0', '0' ]
      balanceToken: [ '0', '0' ]
      sigA: ''

"full" thread state::

      contractAddress: '0xCCC0000000000000000000000000000000000000'
      user: '0xAAA0000000000000000000000000000000000000'
      sender: '0x2220000000000000000000000000000000000000'
      receiver: '0x3330000000000000000000000000000000000000'
      balanceWei: [ '1', '2' ]
      balanceToken: [ '3', '4' ]
      txCount: 22
      sigA: 'sigA0000000000000000000000000000000000000000000000000000000000'

1. All operations support "shorthands" for values; internally, balanceWei: [5, 10] is expanded to balanceWeiHub: 6, balanceWeiUser: 9. This is done through two functions: expandChannelSuccinct, expandThreadSuccinct, which expands the fields in a "succinct" state to a verbose state, and makeSuccinctChannel and makeSuccinctThread, which do the opposite.

   Note that these functions can accept partial states, and combinations of succinct and verbose states.

   Additionally, they will always normalize numeric values to strings.

   For example:

      > verbose = expandSuccinctChannel({
      .   balanceWei: [6, 9],
      .   balanceTokenUser: 69,
      .   timout: 5,
      . })
      > verbose
      {
        balanceWeiHub: '6',
        balanceTokenUser: '9',
        balanceTokenUser: '69',
        timeout: 5,
      }
      > makeSuccinctChannel(verbose)
      {
        balanceWei: ['6', '9'],
        balanceToken: ['0', '69'],
        timeout: 5,
     }

Additionally, useful helper functions:

• mkAddress(prefix): Generates an address by suffixing prefix with zeros::

   > mkAddress('0x1234')
   '0x1234000000000000000000000000000000000000'

• mkHash(prefix): Generates a hash by suffixing prefix with zeros::

   > mkHash('0xab')
   '0xab00000000000000000000000000000000000000000000000000000000000000'