data-structures-es6/test/LinkedList.spec.js

JavaScript data structures written in es6 (es 2015)

'use strict'

let expect = require('expect')
let LinkedList = require('./../index.js').LinkedList

describe('LinkedList', () => {
  let list

  beforeEach(() => {
    list = new LinkedList()
  })

  describe('#push', () => {
    it('check push', () => {
      list.push(1)
      let firstNode = list.head
      expect(firstNode).toEqual(list.head)
      expect(firstNode).toEqual(list.tail)
      expect(firstNode.data).toBe(1)

      list.push(2)
      let secondNode = list.head.next
      expect(secondNode.data).toBe(2)
      expect(secondNode).toEqual(list.tail)

      list.push(3)
      let thirdNode = list.head.next.next
      expect(thirdNode).toEqual(list.tail)
      expect(thirdNode.data).toBe(3)
    })
  })

  describe('#length', () => {
    it('should be 0 on emty list', () => {
      expect(list.length).toBe(0)
    })

    it('should be 0 on emty list', () => {
      list.push(1)
      list.push(2)
      list.removeAt(0)
      list.removeAt(0)

      expect(list.length).toBe(0)
    })

    it('should be 2', () => {
      list.push(1)
      list.push(2)
      expect(list.length).toBe(2)
    })
  })

  describe('#head', () => {
    it('should be null on empty list', () => {
      expect(list.head).toBe(null)
    })

    it('should be null on empty list', () => {
      list.push(1)
      list.push(2)
      list.removeAt(0)
      list.removeAt(0)
      expect(list.head).toBe(null)
    })

    it('should be first element', () => {
      list.push(1)
      list.push(2)
      expect(list.head.data).toBe(1)
    })
  })

  describe('#tail', () => {
    it('should be null on emty list', () => {
      expect(list.tail).toBe(null)
    })

    it('should be first item', () => {
      list.push(1)
      expect(list.tail.data).toBe(1)
    })

    it('should be last item in list', () => {
      list.push(1)
      list.push(2)
      expect(list.tail.data).toBe(2)
    })

    it('should changed after removing', () => {
      list.push(1)
      list.push(2)
      list.removeAt(1)
      expect(list.tail.data).toBe(1)
      list.removeAt(0)
      expect(list.tail).toBe(null)
    })
  })

  describe('#at', () => {
    it('check existing elements', () => {
      list.push(1)
      list.push(2)
      list.push(3)

      expect(list.at(0).data).toBe(1)
      expect(list.at(1).data).toBe(2)
      expect(list.at(2).data).toBe(3)
    })

    it('position less than 0', () => {
      list.push(1)

      expect(() => {
        list.at(-1)
      }).toThrow()
    })

    it('position bigger than exist', () => {
      list.push(1)

      expect(() => {
        list.at(1)
      }).toThrow()
    })
  })

  describe('#removeAt', () => {
    it('remove first node', () => {
      list.push(1)
      list.push(2)
      list.removeAt(0)

      expect(list.head.data).toBe(2)
      expect(list.length).toBe(1)
    })

    it('remove last node', () => {
      list.push(1)
      list.push(2)
      list.removeAt(1) //second element

      expect(list.tail.data).toBe(1)
      expect(list.length).toBe(1)
    })

    it('remove node in the middle', () => {
      list.push(1)
      list.push(2)
      list.push(3)
      list.removeAt(1) //second element

      expect(list.at(1).data).toBe(3)
      expect(list.length).toBe(2)
    })

    it('remove not existed node', () => {
      list.push(1)

      expect(() => {
          list.removeAt(1)
      }).toThrow()

    })
  })

  describe('#current', () => {
    it('should be null on empty list', () => {
      expect(list.current).toBe(null)
    })

    it('should be first element', () => {
      list.push(1)
      list.push(2)

      expect(list.current.data).toBe(1)
    })

    it('should be second element', () => {
      list.push(1)
      list.push(2)
      list.next()

      expect(list.current.data).toBe(2)
    })

    it('should be last element', () => {
      list.push(1)
      list.push(2)
      list.next()
      list.next()
      list.next()

      expect(list.current.data).toBe(2)
    })
  })

  describe('#next', () => {
    it('should return next element', () => {
      list.push(1)
      list.push(2)

      let next = list.next()
      expect(next.data).toBe(2)
    })

    it('if next element doen\'t exist return null', () => {
      list.push(1)
      list.push(2)

      list.next()
      let nextNext = list.next()
      expect(nextNext).toBe(null)
    })
  })

  describe('#resetCursor', () => {
    it('should be null on empty list', () => {
      list.push(1)
      list.removeAt(0)
      list.resetCursor()

      expect(list.current).toBe(null)
    })

    it('should be first element on non empty list', () => {
      list.push(1)
      list.push(2)
      list.next()
      list.resetCursor()
      expect(list.current.data).toBe(1)
    })
  })
})