tdfjs is an experimental runner-less TDD tool for JavaScript.

With npm:

npm install tdfjs

• Minimialistic. 2.2k minified/0.9k gziped.
• No test-runner, evaluating the code verifies the behavior.
• Suitable for testing front end prototypes, e.g. codepen.io, jsbin.com, jsfiddle.net.
• Focuses tests the smallest unit of work – a single function.
• Syntax places emphasis on test-first approach.
• Couples requirements and implemention.

var add = tdf("A function that adds multiple numbers")
  .when(1,1).returns(2)
  .when(2,2).returns(4)
  .when(5,-1).returns(4)
  .when(1,1,1).returns(3)
  .when(1).returns(1)
  .when(0.5,0.5,1).returns(2)
  .define(function() {
    var sum = 0;
    for(var i = 0; i < arguments.length; i++) {
      sum += arguments[i];
    }
    return sum;
  });

• Proclaim – A fantastic, minimal assertion library.

• Test quality evaluation – analyze tests cases/arguments and warn if there are cases where behavior is not defined.
• Allow multiple function defintions that resolve a particular set of requirements, with the ability to swap between them.
• Production switch that turns off all validation for higher performance at the obvious cost of validation.