mocha: The same test suite won't run twice when using mocha programmatically

So I definitely had to solve this problem at least once before, yet tonight I could not remember how, so here is an example to assist my future self (or anyone else 😃 ):

function runMochaTests() {
    Object.keys( require.cache ).forEach( function( file ) {
        delete require.cache[ file ];
    } );

    var mocha = new Mocha();

    mocha.addFile( 'run_test.js' );

    mocha.run();
}

Its ugly, but you should be able to call runMochaTests() multiple times.

Deleting the cache right after running require() seems to do nicely. I suspect it’s very racy but I’ve been able to run the test hundreds of time in parallel.

let mocha = new Mocha({});

mocha.suite.on('require', function (global, file) {
    delete require.cache[file];
});

//TODO: add files to suite & do things

mocha.run();

How do I run tests more than once?

var Mocha = require('mocha');
var mocha = new Mocha({});
mocha.addFile('test.js');
mocha.run();

setTimeout(function() {
    mocha.run();
},1000);

Output is something like:

  suite
    √ test


  1 passing (11ms)



  suite
    1) test


  0 passing (16ms)
  1 failing

  1) suite test:
     TypeError: Cannot read property 'call' of undefined
      at callFn (node_modules\mocha\lib\runnable.js:334:20)
      at Test.Runnable.run (node_modules\mocha\lib\runnable.js:327:7)
      at Runner.runTest (node_modules\mocha\lib\runner.js:429:10)
      at node_modules\mocha\lib\runner.js:535:12
      at next (node_modules\mocha\lib\runner.js:349:14)
      at node_modules\mocha\lib\runner.js:359:7
      at next (node_modules\mocha\lib\runner.js:285:14)
      at Immediate.<anonymous> (node_modules\mocha\lib\runner.js:327:5)

If anyone comes across this post and is trying to run mocha tests in your browser, here is what I did to reset the tests after mocha.run()

const resetTests = () => {
  mocha.suite.suites = []
  let testSpecs = document.getElementById('testSpecs')
  if (testSpecs) testSpecs.remove()
  testSpecs = document.createElement('script')
  testSpecs.src = '/questions-specs/testSpecs.js'
  testSpecs.async = true
  testSpecs.id = 'testSpecs'
  document.body.appendChild(testSpecs)
}

setTimeout(resetTests, 1000)

Faced the same issue, and options above have not worked for me. I just created a helper MochaRunner class and now I can rerun the same tests.

// Usage
const runner1 = new MochaRunner();
const runner2 = new MochaRunner();

runner1.run(['test1.js', 'test2.js']).then(() => {
   runner1.cleanup();
});

runner2.run(['test1.js']).then(() => {
   runner2.cleanup();
})

and in both cases test1.js will be run!

P.S. Hope it will help to someone 😉

I almost lost all of my hair. The issue is stated at the bottom of the ‘angelo’ npm module description, https://www.npmjs.com/package/angelo.

The test files are being loaded with a require, which is being cached. A simple fix would be to remove the test files cached after each run. I wouldn’t consider this hacky.

For my own quick workaround, I’m just calling delete require.cache[testFileName] before addFile(testFileName).

Hello.

The solution from @traviswimer is not working. My mocha tests are running only once. I can not debug it. I dont now solution.

Deleting the require.cache did not work for me. Spawning a child process did. For my use case, here was the before and after: BEOFRE:

const testFile = (filename, reporter) => {
    if (filename.includes('.test.js')) {
        const output = [];
        const mocha = new Mocha({ reporter: reporter });
        delete require.cache[filename]
        mocha.addFile(filename);

        return new Promise((resolve, reject) => {
            mocha.run(failures => {
                resolve(failures);
            })
        })
    }
};

AFTER:

const spawn = require('child-process-promise').spawn;

const testFile = (filename, reporter) => {
    if (filename.includes('.test.js')) {
        const output = [];
        const promise = spawn('mocha', ['-R', reporter, filename], {stdio: "inherit"})

        return new Promise((resolve, reject) => {
            promise
                .then(() => resolve(0))
                .catch((err) => {resolve(1) })
        })
    }
};