Test a command

A unit test for a command looks like this:

import { getEventBridgeMock, getLoggerMock, safeBind } from '@purista/core'
import { createSandbox } from 'sinon'

import { pingV1Service } from '../../pingV1Service'
import { fooCommandBuilder } from './fooCommandBuilder'

describe('service Ping version 1 - command foo', () => {
  let sandbox = createSandbox()
  beforeEach(() => {
    sandbox = createSandbox()
  })

  afterEach(() => {
    sandbox.restore()
  })

  test('does not throw', async () => {
    const service = await pingV1Service.getInstance(
      getEventBridgeMock(sandbox).mock, 
      { 
        logger: getLoggerMock(sandbox).mock 
      }
    )

    // use safeBind to keep the typescript types
    const foo = safeBind(fooCommandBuilder.getCommandFunction(), service)
    // alternative without
    // const foo = fooCommandBuilder.getCommandFunction().bind(service)

    const payload: Parameters<typeof foo>[1] = {}

    const parameter: Parameters<typeof foo>[2] = {}

    // get a mocked command context
    const context = fooCommandBuilder.getCommandContextMock({
      payload,
      parameter,
      sandbox,
      resources: service.resources,
    })

    // execute the command including the validations and hooks
    const result = await foo(context.mock, payload, parameter)

    expect(result).toStrictEqual({ foo: 'foo' })
  })
})

The interesting part is the mocked command context.
The getCommandContextMock method of the command builder returns an object, which has two entries.

The mock entry is the mocked context, which can be passed to the command function.

The stubs entry contains Sinon stubs for every context method.

As an example, a command might invoke other services and we need to mock the returned data.

const context = fooCommandBuilder.getCommandContextMock({payload, parameter, sandbox})

context.stubs.service.OtherService[1].otherCommand.resolves('mock data')

Testing

During unit tests, you will need to mock command invokes.
PURISTA provides the getCommandContextMock in the command builder, which allows you to easily mock service invocations.

Only services defined with canInvoke are available in the context mock.

const context = fooCommandBuilder.getCommandContextMock({payload, parameter, sandbox})

// type/autocomplete is done magically
context.stubs.service.OtherServiceName[1].otherCommandName.resolves({ resultValue: 'the mocked value' })