@onflow/flow-js-testing/examples/05-emulator-management.test.js

This package will expose a set of utility methods, to allow Cadence code testing with libraries like Jest

import path from "path"
import {emulator, init, executeScript} from "../src"

beforeEach(async () => {
  const basePath = path.resolve(__dirname, "./cadence")

  await init(basePath)

  // Let's enable logging initially
  const logging = true

  // Enable only debug messages
  // emulator.addFilter("debug");
  // emulator.addFilter("service");
  emulator.addFilter("info")

  // Start emulator instance on available ports
  await emulator.start({logging})
})

// eslint-disable-next-line jest/expect-expect
test("emulator management", async () => {
  // Let's define simple method to log message to emulator console
  const logMessage = async message => {
    return executeScript({
      code: `
        access(all) fun main(){
          log("------------> ${message}")
        }
      `,
    })
  }
  // This line will be visible in emulator output
  emulator.setLogging(true)
  await logMessage("Now you see me...")

  // Next turn it OFF
  emulator.setLogging(false)
  // Next log will not be visible in emulator output
  await logMessage("NOW YOU DON'T!")

  // And ON back again
  emulator.setLogging(true)
  await logMessage("Easy right?")

  // Now let's disable debug messages and only show "info" messages
  emulator.clearFilters()
  await logMessage("this won't be visible as well")

  // Then silently turn it off
  emulator.setLogging(false)
})

afterEach(async () => {
  // Stop running emulator
  await emulator.stop()
})