Mocha test runner with external files - hooks run in different order? - node.js

Question

I am trying to organise my mocha tests to run through a separate test runner. Whenever I run the test, console.log outputs a proper connection in the top level before block, but straight after outputs me null in the separate required file it block. The hook is being executed, and it sets the connection variable correctly, but somehow it does not get passed to the required file.
How come the connection does not get properly set? Confusingly, according to my debugger it block is executed before the before hook which contradicts the order of console.logs I see
describe.only('test-suite', async () => {
let connection; // undefinded at this point
before(async () => {
connection = await getConnection();
console.log(connection); -> proper connection instance
});
after(async () => {
await closeConnection();
});
require('./some/test')(
connection
);
});
./some/test.js
module.exports = async (
connection,
) => {
describe('my-method', async () => {
it('does things', async () => {
console.log(connection); // somehow undefined
});
});
};

Answer 1

This is because of the way JS handles references to objects. Reassigning the variable does not just change the value the reference points to, but instead creates a brand new reference pointing to a brand new value.
This is the workaround:
describe.only('test-suite', async () => {
let options = { connection: null};
before(async () => {
options.connection = await getConnection();
console.log(connection);
});
after(async () => {
await closeConnection();
});
require('./some/test')(
options
);
});
./some/test.js
module.exports = async (
options,
) => {
describe('my-method', async () => {
it('does things', async () => {
console.log(options.connection);
});
});
};