Provide example using database with 100% test coverage

[mandaputtra]

Hi, fastify are great framework (Thanks for everything ❤️ ) I use it a lot ~ however this is my first time writing test for my HTTP API haha. I didn't seems to found any example on the internet on how to achieve 100% coverage in integration test. Because sometimes error are harder to replicate, so it need mock. With this following example :

  app.post("/", async (request, reply) => {
    try {
      const { body } = request;
      const book = await create(body.title);
      reply.send(book.rows);
    } catch (error) {
      reply.code(500).send({ message: "internal server error" });
    }
  });

Lest say the create() function will only throw error if you lost your connection to a database, catch(error) block will never be covered on test. Thanks to one of the fastify maintainer that answering my question on SO I now able to test achieve 100% coverage! 💯

Therefore I want to place the example here, so that everyone search it can found it easily.

Checklist

• run npm run test and npm run benchmark
• tests and/or benchmarks are included
• documentation is changed or added
• commit message and code follows the Developer's Certification of Origin
  and the Code of conduct

[mcollina]

I think this needs a few improvements.

1. use fastify-postgres instead of manually instantiating a pool.
2. add 'use strict' everywhere
3. have tests that actually test the database queries

[mandaputtra]

I updated the code to be like this, but now it will be hard to mock and return error since I must create whole fastify object with t.mock any suggestion?

  app.get("/", async (_request, reply) => {
    try {
      const client = await app.pg.connect();
      const { rows } = await client.query("SELECT * FROM books");
      client.release();
      reply.send(rows);
    } catch (error) {
      reply.code(500).send(error.message);
    }
  });

[mcollina]

I would recommend the following:

fastify.post('/user/:username', (req, reply) => {
  // will return a promise, fastify will send the result automatically
  return fastify.pg.transact(async client => {
    // will resolve to an id, or reject with an error
    const id = await client.query('INSERT INTO users(username) VALUES($1) RETURNING id', [req.params.username])

    // potentially do something with id

    return id
  })
})

and remove the try/catch. Note that in case of an error the client is never released

[mandaputtra]

Is it okay that the client never released when error happen?

[mcollina]

Good work! Almost there

[mcollina]

lgtm