Emulator
How to start a new instance of emulator
Flow Javascript Testing Framework exposes emulator singleton allowing you to run and stop emulator instance
programmatically. There are two methods available on it.
emulator.start(options)
Starts emulator on random available port, unless overriden in options. Returns Promise.
Arguments
| Name | Type | Optional | Description |
|---|---|---|---|
options | EmulatorOptions | ✅ | an object containing options for starting the emulator |
EmulatorOptions
| Key | Type | Optional | Description |
|---|---|---|---|
logging | boolean | ✅ | whether log messages from emulator shall be added to the output (default: false) |
flags | string | ✅ | custom command-line flags to supply to the emulator (default: "") |
adminPort | number | ✅ | override the port which the emulator will run the admin server on (default: auto) |
restPort | number | ✅ | override the port which the emulator will run the REST server on (default: auto) |
grpcPort | number | ✅ | override the port which the emulator will run the GRPC server on (default: auto) |
Returns
| Type | Description |
|---|---|
| Promise | Promise, which resolves to true if emulator started successfully |
Usage
import {emulator, init} from "@onflow/flow-js-testing"
describe("test setup", () => {
// Instantiate emulator and path to Cadence files
beforeEach(async () => {
const basePath = path.resolve(__dirname, "../cadence")
await init(basePath)
// Start emulator instance on auto-selected available ports
await emulator.start()
})
})
emulator.stop()
Stops emulator instance. Returns Promise.
Arguments
This method does not expect any arguments.
Usage
import {emulator, init} from "@onflow/flow-js-testing"
describe("test setup", () => {
// Instantiate emulator and path to Cadence files
beforeEach(async () => {
const basePath = path.resolve(__dirname, "../cadence")
await init(basePath)
await emulator.start()
})
// Stop emulator, so it could be restarted
afterEach(async () => {
await emulator.stop()
})
})
emulator.setLogging(newState)
Set logging flag on emulator, allowing to temporally enable/disable logging.
Arguments
| Name | Type | Description |
|---|---|---|
newState | boolean | Enable/disable logging |
Usage
import {emulator, init} from "@onflow/flow-js-testing"
describe("test setup", () => {
// Instantiate emulator and path to Cadence files
beforeEach(async () => {
const basePath = path.resolve(__dirname, "../cadence")
await init(basePath)
await emulator.start()
})
// Stop emulator, so it could be restarted
afterEach(async () => {
await emulator.stop()
})
test("basic test", async () => {
// Turn on logging from begining
emulator.setLogging(true)
// some asserts and interactions
// Turn off logging for later calls
emulator.setLogging(false)
// more asserts and interactions here
})
})