🚀 Feature: Global fixtures should run before any files are loaded

[lucasrcosta]

Prerequisites

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Description

When using global fixtures, mocha loads the test files before running mochaGlobalSetup. This can cause issues when dependencies themselves load top-level configurations . But when --watch is passed, it works as expected.

This behavior differs from the following statements in the documentation:

Work identically parallel mode, watch mode, and serial mode
Now, before Mocha loads and runs your tests, it will execute the above global setup fixture, starting a server for testing.

Steps to Reproduce

fixtures.js

exports.mochaGlobalSetup = function() {
  console.log(`mochaGlobalSetup`);
}

test.js

console.log('Test file loaded')

it('runs', () => { })

Expected behavior:
Should run mochaGlobalSetup before loading the test files in all cases.

Actual behavior: [What actually happens]

> npx mocha -r fixtures.js test.js
Test file loaded
mochaGlobalSetup

  ✓ runs

  1 passing (3ms)

> npx mocha -r fixtures.js test.js --watch
mochaGlobalSetup
Test file loaded

  ✓ runs

  1 passing (2ms)

ℹ [mocha] waiting for changes...

Reproduces how often: 100%

Versions

• node --version: Unknown command: mocha
• node node_modules/.bin/mocha --version: 8.2.1
• node --version: v10.22.1
• Your operating system: macOS Catalina 10.15.7 64bit
• Your shell (e.g., bash, zsh, PowerShell, cmd): fish

[boneskull]

This is intended behavior, but

1. the documentation is correct in that the fixtures are run before your tests
2. it is incorrect in that the fixtures are not run before your test files load

the reason it is the way it is: it'd otherwise be unusable in a browser without adding more API surface, and we try to keep things the same between node/browser as much as possible.

this will be a problem if we allow async suites, since the suites would potentially try to use a resource (e.g. connect to a port) that a global setup fixture created... hm.

two questions:

1. does this behavior prevent you from using global fixtures?
2. if you used it as it works now, and we changed global setup fixtures to run before the test files are loaded, would that break what you're doing?

[boneskull]

I've created #4511 to address this. I agree that the behavior should change. Hopefully there hasn't been too much adoption of the feature yet..

[lucasrcosta]

@boneskull thank you for addressing this.

1. does this behavior prevent you from using global fixtures?

It does, since the test files are loaded before the fixtures. I'm working in a codebase that loads configurations from a database before importing the files to start a webserver. Some of it's dependencies use these configurations on top-level code (regardless of wether that's good practice or not), so today I cannot push global fixtures to the code since it would break the CI workflow.

2. if you used it as it works now, and we changed global setup fixtures to run before the test files are loaded, would that break what you're doing?

No, in fact the behavior on watch mode is exactly that, so I've been developing that way the last few days. I understand I'll have to revert the introduction of global fixtures and wait for this to be finished in order to adopt it.

By the way, this is a great feature and it makes the test setup process so much clearer. Specially if you can delay the files being loaded, so that all code can be in the proper place. Congratulations.

[SgtPooki]

I left a comment saying the setup and teardown functions weren't being called for me, they are.. I was doing

exports = {
    mochaGlobalSetup,
    mochaGlobalTeardown,
    mochaHooks,
};

instead of

exports.mochaGlobalSetup = mochaGlobalSetup;
exports.mochaGlobalTeardown = mochaGlobalTeardown;
exports.mochaHooks = mochaHooks;

too used to typescript ¯_(ツ)_/¯. Hopefully leaving this comment helps someone else?

[witrin]

Without this patch we were currently not able to perform integration tests for one of our bigger systems in a clean and lean way. We really hope for a merge here. Because 9 is already released.

[witrin]

@boneskull How is the planing about this?

[mariobm]

This feature would be a game-changer for me. It's really needed.

[justinasfour04]

what is the status on this? I need this fix in version 8.2.0

[justinasfour04]

This issue is 2 years old, does anyone have a work-around?

[codembark]

This prevents me from using global fixtures to set up integration tests. My use case is starting a database before importing a server module in the test file which requires the database to exist. I'll have to find another work around in the meantime.

Appreciate all the hard work you folks put into Mocha!