message: fixed ReferenceError: TextEncoder is not defined
diff: import { toContainGraph } from '../custom-matchers/toContainGraph'
  import { toEqualGraph } from '../custom-matchers/toEqualGraph'
  import { error, log, trace, warn } from '../../src/debug'
  +import { TextEncoder, TextDecoder } from 'util'
  +global.TextEncoder = TextEncoder
  +global.TextDecoder = TextDecoder
  // We don't want to output debug messages to console as part of the tests
  jest.mock('../../src/debug')
  