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Testing a client application

Testing a client application can be a crucial part of ensuring its functionality and performance. When it comes to TypeScript projects, you can utilize the createRouterTransport method from @bufbuild/connect to create a mock transport that can be used in both backend and frontend applications.

For frontend applications, it may not always be feasible or desirable to test against an actual API. In such cases, you can utilize a mocked Connect backend to test your application.

A simple mock for Eliza

To illustrate, let's write a test for ELIZA that uses createRouterTransport:

import { createRouterTransport } from '@bufbuild/connect';
import { ElizaService } from '@buf/bufbuild_eliza.bufbuild_connect-es/buf/connect/demo/eliza/v1/eliza_connect';
import { SayResponse } from '@buf/bufbuild_eliza.bufbuild_connect-es/buf/connect/demo/eliza/v1/eliza_pb';

export const mockElizaTransport = () =>
createRouterTransport(({ service }) => {
service(ElizaService, {
say: () => new SayResponse({ sentence: 'I feel happy.' })

In your client testing code, you can then use createPromiseClient from @bufbuild/connect with mockElizaTransport:

import { createPromiseClient } from '@bufbuild/connect';

describe('your client test suite', () => {
it('tests a simple client call', async () => {
const client = createPromiseClient(ElizaService, mockElizaTransport());
const { sentence } = await client.say({ sentence: 'how do you feel?' });
expect(sentence).toEqual('I feel happy');

Learning more about client testing

See the Connect-Node documentation to learn about: