test(cli): add simulate function test case

cli/src/__tests__/utils/simulate.test.ts

@@ -0,0 +1,73 @@
+import { loadSimulator } from '../../utils/simulate'
+import { expect, describe, it, jest, beforeEach } from '@jest/globals'
+import * as path from 'path'
+
+jest.mock('fs', () => ({
+  existsSync: jest.fn().mockReturnValue(true),
+  readdirSync: jest.fn().mockReturnValue(['IEM.js', 'tesla.js']),
+  statSync: jest.fn().mockReturnValue({ birthtime: new Date() }),
+}))
+
+const actualPath = jest.requireActual('path')
+jest.mock('path', () => {
+  const actualPath = jest.requireActual('path') as typeof import('path')
+  return {
+    ...actualPath,
+    join: jest.fn().mockImplementation((...args: any[]) => actualPath.join(...args)),
+    resolve: jest.fn().mockImplementation((...args: any[]) => actualPath.resolve(...args)),
+  }
+})
+
+describe('loadSimulator', () => {
+  const mockGenerator = jest.fn()
+  const mockSimulatorModule = {
+    generator: mockGenerator,
+    name: 'IEM',
+    author: 'EMQX Team',
+    dataFormat: 'JSON',
+    version: '1.0.0',
+    description: 'Test simulator description',
+  }
+
+  beforeEach(() => {
+    jest.resetModules()
+    const scenarioPath = path.join(__dirname, '../../scenarios/IEM.js')
+    jest.doMock(scenarioPath, () => mockSimulatorModule, { virtual: true })
+  })
+
+  it('should load a simulator successfully', () => {
+    const simulator = loadSimulator('IEM')
+
+    expect(simulator).toEqual({
+      ...mockSimulatorModule,
+      generator: expect.any(Function),
+      file: undefined,
+      realFilePath: expect.stringContaining('IEM.js'),
+    })
+
+    const options: any = { clientId: 'test', count: 1 }
+    simulator.generator(options)
+    expect(mockGenerator).toHaveBeenCalledWith(expect.any(Object), options)
+  })
+
+  it('should throw an error for invalid file type', () => {
+    expect(() => loadSimulator('invalidFile', 'invalid.txt')).toThrow('Invalid file type')
+  })
+
+  // it('should throw an error for non-existent file', () => {
+  //   const fs = require('fs')
+  //   fs.existsSync.mockReturnValueOnce(false)
+  //   expect(() => loadSimulator(undefined, 'nonexistent.js')).toThrow((error: Error) => {
+  //     expect(error).toBeInstanceOf(Error)
+  //     expect(error.message).toMatch(/Load simulator error: Error: Cannot find module/)
+  //     expect(error.message).toContain('nonexistent.js')
+  //     return true
+  //   })
+  // })
+
+  it('should throw an error for invalid simulator module', () => {
+    const invalidModulePath = path.join(__dirname, '../../scenarios/invalidModule.js')
+    jest.doMock(invalidModulePath, () => ({}), { virtual: true })
+    expect(() => loadSimulator('invalidModule')).toThrow('Not a valid simulator module')
+  })
+})