ensure invalid arguments are not ignored when using bin/mocha; closes #3687

[boneskull]

What was happening here was that yargs-parser's default command does error checking but does not return the errors. instead, it would act like no such argument was provided. this means that if you used --ui, it would act as if you passed nothing, then go and grab whatever the default is (in this case, bdd).

using the detailed() function of yargs-parser solves this problem.

added a test

[coveralls]

Coverage increased (+0.01%) to 91.082% when pulling 8f15365 on boneskull/issue/3687 into 0899fdd on master.

[plroebuck]

Test filename is misleading since the option arguments are not invalid, but missing.

More comprehensive version of your test...

describe('options requiring unprovided argument', function() {

  function getOptionsNeedingArgument() {
    const options = [];
    const types = require('../../cli/run-option-metadata').types;
    delete types.boolean;
    Object.keys(types).forEach((type) => types[type].forEach((option) => {
      options.push(option);
    }));
    return options.sort();
  }

  const options = getOptionsNeedingArgument();
  options.forEach((option) => {
    return function() {
      const optFlag = `--${option}`;
      it(`should exit with failure if option ${optFlag} given without argument`, function(done) {
        const args = [optFlag];
        const spawnOpts = {stdio: 'pipe'};
        invokeMocha(
          args,
          function(err, result) {
            if (err) {
              return done(err);
            }
            expect(result, 'to have failed');
            expect(result.output, 'to match', /not enough arguments/i);
            done();
          },
          spawnOpts
        );
      });
    };
  });
});