class.js

    TimeRange.prototype.getEnd = function() {
      var end = this.end;
      if (end) {
        return end;
      } else {
        return parseInt(this.start) + 3600 // 1 hour
      }
    };

spec.js

  describe('#getEnd', function() {
    describe('when end is defined', function() {
      it('returns end', function() {
        var timeRange = new TimeRange({end: 1390089600});

        expect(timeRange.getEnd()).toBe(1390089600);
      });
    });

    describe('when end is undefined', function() {
      it('returns start plus one hour', function() {
        var timeRange = new TimeRange({start: 1390089600});

        expect(timeRange.getEnd()).toBe(1390093200);
      });

      it('coerces start into an integer', function() {
        var timeRange = new TimeRange({start: '1390089600'});

        expect(timeRange.getEnd()).toBe(1390093200);
      });
    });
  });