metamask-extension/test/unit/app/controllers/cached-balances-test.js

const assert = require('assert')
const sinon = require('sinon')
const CachedBalancesController = require('../../../../app/scripts/controllers/cached-balances')

describe('CachedBalancesController', () => {
  describe('updateCachedBalances', () => {
    it('should update the cached balances', async () => {
      const controller = new CachedBalancesController({
        getNetwork: () => Promise.resolve(17),
        accountTracker: {
          store: {
            subscribe: () => {},
          },
        },
        initState: {
          cachedBalances: 'mockCachedBalances',
        },
      })

      controller._generateBalancesToCache = sinon.stub().callsFake(() => Promise.resolve('mockNewCachedBalances'))

      await controller.updateCachedBalances({ accounts: 'mockAccounts' })

      assert.equal(controller._generateBalancesToCache.callCount, 1)
      assert.deepEqual(controller._generateBalancesToCache.args[0], ['mockAccounts', 17])
      assert.equal(controller.store.getState().cachedBalances, 'mockNewCachedBalances')
    })
  })

  describe('_generateBalancesToCache', () => {
    it('should generate updated account balances where the current network was updated', () => {
      const controller = new CachedBalancesController({
        accountTracker: {
          store: {
            subscribe: () => {},
          },
        },
        initState: {
          cachedBalances: {
            17: {
              a: '0x1',
              b: '0x2',
              c: '0x3',
            },
            16: {
              a: '0xa',
              b: '0xb',
              c: '0xc',
            },
          },
        },
      })

      const result = controller._generateBalancesToCache({
        a: { balance: '0x4' },
        b: { balance: null },
        c: { balance: '0x5' },
      }, 17)

      assert.deepEqual(result, {
        17: {
          a: '0x4',
          b: '0x2',
          c: '0x5',
        },
        16: {
          a: '0xa',
          b: '0xb',
          c: '0xc',
        },
      })
    })

    it('should generate updated account balances where the a new network was selected', () => {
      const controller = new CachedBalancesController({
        accountTracker: {
          store: {
            subscribe: () => {},
          },
        },
        initState: {
          cachedBalances: {
            17: {
              a: '0x1',
              b: '0x2',
              c: '0x3',
            },
          },
        },
      })

      const result = controller._generateBalancesToCache({
        a: { balance: '0x4' },
        b: { balance: null },
        c: { balance: '0x5' },
      }, 16)

      assert.deepEqual(result, {
        17: {
          a: '0x1',
          b: '0x2',
          c: '0x3',
        },
        16: {
          a: '0x4',
          c: '0x5',
        },
      })
    })
  })

  describe('_registerUpdates', () => {
    it('should subscribe to the account tracker with the updateCachedBalances method', async () => {
      const subscribeSpy = sinon.spy()
      const controller = new CachedBalancesController({
        getNetwork: () => Promise.resolve(17),
        accountTracker: {
          store: {
            subscribe: subscribeSpy,
          },
        },
      })
      subscribeSpy.resetHistory()

      const updateCachedBalancesSpy = sinon.spy()
      controller.updateCachedBalances = updateCachedBalancesSpy
      controller._registerUpdates({ accounts: 'mockAccounts' })

      assert.equal(subscribeSpy.callCount, 1)

      subscribeSpy.args[0][0]()

      assert.equal(updateCachedBalancesSpy.callCount, 1)
    })
  })

})