There are several gulp tasks defined in gulpfile.js.
The gulp task less will compile any less files in the less/compile folder to css and minified css and output them to the css folder.
Run watch-less while developing to compile css as changes are made.
Front-end js is compiled using Webpack, with entry point js/entry.js and output js/bundle.js. Run the gulp watch-bundle task while developing to compile the js.
Tests
Tests are written in Jasmine.
Tests are run by Karma with a Webpack preprocessor - details in ./karma.config.js
To run tests once run npm test.
For developing, npm install karma-cli -g and then run karma start in the app directory.