Is there a way to inject dependencies into Context for testing?

[hiroki23]

I have some code as follows:

import { Hono } from "hono";

const app = new Hono();

app.get("/", async (c) => {
	const user = c.get("currentUser");
	return c.json({ id: user.id, name: user.name });
});

export default app;

I'm thinking that testing would be much simpler if I could inject dependencies into the Context.
Is there a way to do this?

[bard]

Create a testApp that has test dependencies initialized via a middleware and mount your app onto it. Example:

app.ts:

import { Hono } from "hono";
import type { Logger } from "pino";

export type Deps = {
  logger: Logger;
};

export const app = new Hono<{
  Variables: Deps;
}>();

app.get("/ping", (c) => {
  c.get("logger").info("pinging");

  return c.json({ pong: true });
});

app.test.ts:

import { Hono } from "hono";
import type { Logger } from "pino";
import { expect, test, vi } from "vitest";
import { type Deps, app } from "./app.js";

const getAppWithMockedDeps = () => {
  const testDeps = {
    logger: {
      info: vi.fn(),
    } as unknown as Logger,
  };

  const appWithTestDeps = new Hono<{ Variables: Deps }>();
  appWithTestDeps
    .use(async (c, next) => {
      c.set("logger", testDeps.logger);
      await next();
    })
    .route("/", app);

  return { app: appWithTestDeps, deps: testDeps };
};

test("logs when pinging", async () => {
  const { app, deps } = getAppWithMockedDeps();

  await app.request("/ping");

  expect(deps.logger.info).toHaveBeenCalled();
});

@yusukebe would be nice to have something like this in the docs, the ability to test handlers without starting a server was one of the things that attracted me to Hono, but when it was time to write tests, it wasn't at all obvious how to inject dependencies.