ramda-fantasy/test/reader.test.js

var assert = require('assert');
var types = require('./types');

var Reader = require('..').Reader;

function add(a) {
  return function(b) { return a + b; };
}

function always(x) {
  return function() { return x; };
}

function mult(a) {
  return function(b) { return a * b; };
}

function identity(x) { return x; }

describe('Reader properties', function() {

  var f1 = function(x) { return x + '1 '; };
  var f2 = function(x) { return x + '2 '; };
  var f3 = function(x) { return x + '3 '; };
  var r1 = Reader(f1);
  var r2 = Reader(f2);

  it('is a Functor', function() {
    var fTest = types.functor;
    assert.ok(fTest.iface(r1));
    assert.ok(fTest.id(r1));
    assert.ok(fTest.compose(r1, f2, f3));
  });

  it('is an Apply', function() {
    var aTest = types.apply;
    var a = Reader(function() { return add(1); });
    var b = Reader(function() { return always(2); });
    var c = Reader(always(4));

    assert.equal(true, aTest.iface(r1));
    assert.equal(true, aTest.compose(a, b, c));
  });

  it('is an Applicative', function() {
    var aTest = types.applicative;

    assert.equal(true, aTest.iface(r1));
    assert.equal(true, aTest.id(Reader, r2));
    assert.equal(true, aTest.homomorphic(r1, add(3), 46));
    assert.equal(true, aTest.interchange(
      Reader(function() { return mult(20); }),
      Reader(function() { return mult(0.5); }),
      73
    ));
  });

  it('is a Chain', function() {
    var cTest = types.chain;
    var c = Reader(function() {
      return Reader(function() {
        return Reader(function() {
          return 3;
        });
      });
    });
    assert.equal(true, cTest.iface(r1));
    assert.equal(true, cTest.associative(c, identity, identity));
  });

  it('is a Monad', function() {
    var mTest = types.monad;
    assert.equal(true, mTest.iface(r1));
  });

  describe('#toString', function() {

    it('returns the string representation of a Reader', function() {
      assert.strictEqual(Reader(function(x) { void x; }).toString(),
                         'Reader(function (x) { void x; })');
    });

  });

});

describe('Reader examples', function() {
  it('should write name of options object', function() {

    var options = {name: 'header'};
    var Printer = {};
    Printer.write = function(x) {
      return '/** ' + x + ' */';
    };

    function getOptionsName(opts) {
      return Reader(function(printer) {
        return printer.write(opts.name);
      });
    }

    var nameReader = getOptionsName(options);

    assert.equal(nameReader.run(Printer), '/** header */');
  });
});