import runs all code from module instead of just the imported function - node.js

Question

This is my index.js file, located in the ./src directory:
import { MongoClient } from "mongodb";
import CharacterDAO from "./dao/character";
import GearDAO from "./dao/gear";
import { startServer } from "./server";
import { seedData } from "./dataSeed";
// connect mongoDb, seed data if needed, run fastify server
export const runServer = async ({ dbUrl, dbName, environment, port }) => {
// test seed data when starting server if running a test suite
if (environment === "test") {
await seedData({
hostUrl: dbUrl,
databaseName: dbName
});
}
await MongoClient.connect(dbUrl, {
poolSize: 50,
useNewUrlParser: true,
useUnifiedTopology: true,
wtimeout: 2500
})
.then(async conn => {
const database = await conn.db(dbName);
// inject database connection into DAO objects
CharacterDAO.injectDB(database);
GearDAO.injectDB(database);
// start the fastify server
startServer(port);
})
.catch(err => {
console.log(err.stack);
// process.exit(1);
});
};
const serverArguments = process.argv.slice(2).map(arg => {
return arg.split("=")[1];
});
const serverOptions = {
dbUrl: serverArguments[0],
dbName: serverArguments[1],
environment: serverArguments[2],
port: serverArguments[3]
};
runServer({
...serverOptions
});
jestconfig.json
{
"transform": {
"^.+\\.(t|j)sx?$": "ts-jest"
},
"testEnvironment": "node",
"testRegex": "(/__tests__/.*|(\\.|/)(test|spec))\\.(jsx?|tsx?)$",
"moduleFileExtensions": ["ts", "tsx", "js", "jsx", "json", "node"]
}
Test script from package.json used to run the test (db credentials are omitted)
"test": "dbUrl=mongodb+srv://sdaw-dsawdad-dsadsawd#cluster0-jopi5.mongodb.net dbName=untitled-combat-game-test environment=test port=4000 jest --config jestconfig.json"
My test file:
import { runServer } from "../index";
beforeAll(async () => {
const serverOptions = {
dbUrl: process.env.dbUrl,
dbName: process.env.dbName,
environment: process.env.environment,
port: process.env.port
};
console.log(serverOptions);
await runServer({
...serverOptions
});
});
describe("mock test", () => {
it("should run a basic test", () => {
expect(true).toBe(true);
});
});
What happens when I run the test:
the test script runs runServer
the index.js file runs runServer
This causes a invalid URI error (since the process.argv referenced in index.js does not include a valid mongodb URI). I double-checked this by commenting out the runServer call at the bottom of my index.js file - and everything runs fine.
Moving the runServer function to a different file and importing it from there also solves the issue. So importing in both index.js and the test file does not result in multiple calls.
What am I doing wrong?

Answer 1

Importing/requiring a file evaluates the code inside of it (read: runs the code inside of it). You're not technically doing anything wrong, but for the purpose of your tests the code as you have written it won't work.
In your index.js file you are executing runServer(). Whenever that file is imported/required, that function call is also run.
Having a start.js file or similar which will actually start your server is a common pattern. This will help you avoid the issue you're experiencing.

Answer 2

I would split the definition of your server and invoking your server into two different files, say server.js and index.js. I will leave the fixing up of the imports to you, but this is the idea:
server.js
// connect mongoDb, seed data if needed, run fastify server
export const runServer = async ({ dbUrl, dbName, environment, port }) => {
// test seed data when starting server if running a test suite
if (environment === "test") {
await seedData({
hostUrl: dbUrl,
databaseName: dbName
});
}
await MongoClient.connect(dbUrl, {
poolSize: 50,
useNewUrlParser: true,
useUnifiedTopology: true,
wtimeout: 2500
})
.then(async conn => {
const database = await conn.db(dbName);
// inject database connection into DAO objects
CharacterDAO.injectDB(database);
GearDAO.injectDB(database);
// start the fastify server
startServer(port);
})
.catch(err => {
console.log(err.stack);
// process.exit(1);
});
};
index.js
import { runServer } from './server';
const serverArguments = process.argv.slice(2).map(arg => {
return arg.split("=")[1];
});
const serverOptions = {
dbUrl: serverArguments[0],
dbName: serverArguments[1],
environment: serverArguments[2],
port: serverArguments[3]
};
runServer({
...serverOptions
});