Point free assertion dream

assertions.js

var R = require('ramda');

// * -> IO
var report = R.bind(console.log, console);

// * -> IO
var reportSuccess = R.compose(report, R.always('Success'));

// * -> * -> IO
var reportFailure = function(expected, actual) {
  report('Failure: Expected ' + expected + ' to be ' + actual);
};

// a -> (a -> b -> IO)
var bindExpectedToMatcher = function(expected) {
  return R.partialRight(R.partial, expected);
};

// a -> {(a -> b -> IO)}
var expect = function(expected) {
  return R.mapObj(bindExpectedToMatcher(expected), matchers);
};

// (a -> b -> Boolean) -> a -> b -> IO
var createMatcher = R.partialRight(R.ifElse, reportSuccess, reportFailure);

var matchers = {};

// (a -> b -> Boolean) -> String -> IO
var addMatcher = function(cond, name) {
  matchers[name] = createMatcher(cond);
};

// {k: (a -> b -> Boolean)} -> {k: (a -> b-> IO)}
var addMatchers = R.mapObjIndexed(addMatcher);

addMatchers({
  toBe: R.eq,
  toEqual: R.eqDeep
});

expect(factorial(0)).toBe(1);
expect(factorial(1)).toBe(1);
expect(factorial(5)).toBe(120);
expect(factorial(6)).toBe(100); // Expected 720 to be 100

expect({}).toBe({}); // Expected [object Object] to be [object Object]
expect({}).toEqual({});