How to mock function using node-tap on fastify inject - node.js

Question

I want to make 100% coverage on this function with node-tap but I can't mock the error part, it always throw
Cannot find module 'create' Require stack: - /home/mptr8/Code/Projects/me/fastify-example/fastify-postgres/test/integration.js
But I have create function on my query.js file, what do I do wrong here? Why it doesn't invoke the method?
t.mock("../query.js", {
create: () => {
throw new Error();
},
});
I also try this combination, because query.js are dependent on db.js. Now the mock error gone but still I'm not getting the error throw from my fastify.inject.
t.mock("../db.js", {
"../query.js": {
create: () => { throw new Error() },
},
});
app.post("/", async (request, reply) => {
try {
const { body } = request;
const book = create(body.title);
reply.send(book);
} catch (error) {
// this part are not covered
reply.code(500).send({ message: "internal server error" });
}
});
here are my complete code. You can see the full code on this github repository.
// server.js
const fastify = require("fastify");
const {
migration,
create,
} = require("./query");
const db = require("./db");
function build(opts = {}) {
const app = fastify(opts);
migration();
app.post("/", async (request, reply) => {
try {
const { body } = request;
const book = create(body.title);
reply.send(book);
} catch (error) {
reply.code(500).send({ message: "internal server error" });
}
});
app.addHook("onClose", (_instance, done) => {
db.close();
done();
});
}
module.exports = build;
// db.js
const { Pool } = require("pg");
const pool = new Pool({
connectionString:
"postgresql://postgres:postgres#localhost:5432/fastify_postgres?schema=public",
});
module.exports = {
query: (text, params) => pool.query(text, params),
close: () => pool.end(),
};
// query.js
const db = require("./db");
async function migration() {
await db.query(`
CREATE TABLE IF NOT EXISTS books (
id serial PRIMARY KEY,
title varchar (255) NOT NULL
)
`);
}
async function create(title) {
return await db.query("INSERT INTO books (title) VALUES ($1)", [title]);
}
module.exports = { migration, create };
// test.js
const tap = require("tap");
const fastify = require("../server");
tap.test("coba", async (t) => {
const app = await fastify();
t.test("should success create books", async (t) => {
const response = await app.inject({
method: "POST",
url: "/",
payload: {
title: "Hello,World!",
},
});
t.equal(response.statusCode, 200);
});
t.test("should throw error", async (t) => {
const app = await fastify();
// it doesn't throw the error :((
t.mock("../query.js", {
create: () => {
throw new Error();
},
});
const response = await app.inject({
method: "POST",
url: "/",
payload: {
title: "Hello,World!",
},
});
t.equal(response.statusCode, 500);
// call app close on last test child to close app and db properly
app.close();
});
});

Answer 1

You should use the returned value by the t.mock function:
const build = t.mock({
"../server": {
"./query.js": {
create: () => { throw new Error() },
}
}
})
const app = await build({})