old_contents: #!/usr/bin/env node
  
  require('./proof')(2, function (step, Strata, tmp, load, serialize, objectify, gather, assert) {
      var strata = new Strata({ directory: tmp, leafSize: 3, branchSize: 3 })
      step(function () {
          serialize(__dirname + '/fixtures/large-leaf.before.json', tmp, step())
      }, function () {
          strata.open(step())
      }, function () {
          strata.mutator('_', step())
      }, function (cursor) {
          step(function () {
              cursor.insert('_', '_', ~ cursor.index, step())
          }, function () {
              cursor.unlock()
          })
      }, function () {
          gather(step, strata)
      }, function (records) {
          assert(records, '_abcdefghijklmnopqrstuvwxyz'.split(''), 'records')
          strata.balance(step())
      }, function () {
          objectify(tmp, step())
          load(__dirname + '/fixtures/large-leaf.after.json', step())
      }, function (actual, expected) {
          assert(actual, expected, 'split')
          strata.close(step())
      })
  })
  
new_contents: #!/usr/bin/env node
  
  require('./proof')(2, function (step, Strata, tmp, load, serialize, vivify, gather, assert) {
      var strata = new Strata({ directory: tmp, leafSize: 3, branchSize: 3 })
      step(function () {
          serialize(__dirname + '/fixtures/large-leaf.before.json', tmp, step())
      }, function () {
          strata.open(step())
      }, function () {
          strata.mutator('_', step())
      }, function (cursor) {
          step(function () {
              cursor.insert('_', '_', ~ cursor.index, step())
          }, function () {
              cursor.unlock()
          })
      }, function () {
          gather(step, strata)
      }, function (records) {
          assert(records, '_abcdefghijklmnopqrstuvwxyz'.split(''), 'records')
          strata.balance(step())
      }, function () {
          vivify(tmp, step())
          load(__dirname + '/fixtures/large-leaf.after.json', step())
      }, function (actual, expected) {
          assert(actual, expected, 'split')
          strata.close(step())
      })
  })
  
subject: Use `vivify` in `checksum-constructor.t.js`.