The test runner supports a number of run-time options to be passed to. To view all, run the following:

nightwatch --help
Name Shortname default description
--env -e default Which testing environment to use - defined in nightwatch.json
--config -c ./nightwatch.json Path to configuration file; nightwatch.conf.js or nightwatch.json are read by default if present. Check the Configuration section.
--test -t Runs only the specified test suite/module. By default the runner will attempt to run all tests in the src_folders settings folder(s) and their subfolders.
--testcase Used only together with --test. Runs the specified testcase from the current suite/module.
--group -g Runs only the specified group or several (comma separated) of tests (subfolder). Tests are grouped by being placed in the same subfolder.
--skipgroup -s Skip one or several (comma separated) group of tests.
--filter -f Specify a filter (glob expression) as the file name format to use when loading the test files.
--tag -a Filter test modules by tags. Only tests that have the specified tags will be loaded.
--skiptags Skips tests that have the specified tag or tags (comma separated).
--retries Retries failed or errored testcases up to the specified number of times. Retrying a testcase will also retry the beforeEach and afterEach hooks, if any.
--suiteRetries Retries failed or errored testsuites (test modules) up to the specified number of times. Retrying a testsuite will also retry the before and after hooks (in addition to the global beforeEach and afterEach respectively), if any are defined on the testsuite.
--timeout Set the global timeout for assertion retries before an assertion fails. The various timeout values are defined in the Globals section.
--reporter -r junit Name of a predefined reporter (e.g. junit) or path to a custom reporter file to use.

The custom reporter interface looks like:
module.exports = {
write(results, options, done) {
  done();
}
};
--output -o tests_output The location where the JUnit XML reports will be saved.
--headless Launch the browser (Chrome or Firefox) in headless mode.
--verbose Shows extended selenium command logging during the session
--help -h Shows this help.
--version -v Shows the version number
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