diff --git a/app/javascript/adminterface/lib/__tests__/has_many.html b/app/javascript/adminterface/lib/__tests__/has_many.html
new file mode 100644
index 00000000..cee83d0e
--- /dev/null
+++ b/app/javascript/adminterface/lib/__tests__/has_many.html
@@ -0,0 +1,14 @@
+<div data-sortable="address">
+  <form class="has-many-list">
+    <fieldset class="has_many_fields">
+      <input type="checkbox" name="[_destroy]" checked>
+      <input type="text" name="[address]" value="Tokyo">
+      <a class="button has_many_remove"></a>
+      <a
+        class="button has_many_add"
+        data-html="<div></div>"
+        data-placeholder="script"
+      ></a>
+    </fieldset>
+  </form>
+</div>
\ No newline at end of file
diff --git a/app/javascript/adminterface/lib/__tests__/has_many.spec.js b/app/javascript/adminterface/lib/__tests__/has_many.spec.js
new file mode 100644
index 00000000..59c19304
--- /dev/null
+++ b/app/javascript/adminterface/lib/__tests__/has_many.spec.js
@@ -0,0 +1,225 @@
+/* eslint-env jest */
+import fs from 'fs'
+import path from 'path'
+import Sortable from 'sortablejs'
+import HasManyClass from '../has_many'
+
+jest.mock('sortablejs')
+
+describe('HasMany', () => {
+  const html = fs.readFileSync(path.resolve(__dirname, './has_many.html'))
+  let element
+
+  const options = {
+    list: '.has-many-list',
+    item: 'fieldset.has_many_fields',
+    addLink: 'a.button.has_many_add',
+    removeLink: 'a.button.has_many_remove',
+    destroyInput: 'input[name$="[_destroy]"]'
+  }
+
+  beforeEach(() => {
+    document.documentElement.innerHTML = html
+    element = document.querySelector('div')
+    global.adminterface = {
+      addObserver: jest.fn()
+    }
+  })
+
+  afterEach(() => {
+    jest.restoreAllMocks()
+  })
+
+  test('constructor initiates correctly', () => {
+    const spyOnBind = jest.spyOn(HasManyClass.prototype, '_bind')
+    spyOnBind.mockImplementation(() => {})
+
+    const HasMany = new HasManyClass(element)
+    expect(HasMany.element).toStrictEqual(element)
+
+    expect(spyOnBind).toHaveBeenCalledTimes(1)
+  })
+
+  test('bind calls bindEvents, initSortable and admininterface', () => {
+    const spyOnBindEvents = jest.spyOn(HasManyClass.prototype, '_bindEvents')
+    spyOnBindEvents.mockImplementation(() => {})
+
+    const spyOnInitSortable = jest.spyOn(HasManyClass.prototype, '_initSortable')
+    spyOnInitSortable.mockImplementation(() => {})
+
+    const HasMany = new HasManyClass(element)
+
+    expect(spyOnBindEvents).toHaveBeenCalledWith(element)
+    expect(spyOnInitSortable).toHaveBeenCalledTimes(1)
+    expect(global.adminterface.addObserver).toHaveBeenCalledTimes(1)
+    expect(global.adminterface.addObserver).toHaveBeenCalledWith(
+      element,
+      HasMany,
+      HasMany.constructor.name,
+      []
+    )
+  })
+
+  test('initSortable assigns new instance of Sortable to sortable property', () => {
+    const spyOnBindEvents = jest.spyOn(HasManyClass.prototype, '_bindEvents')
+    spyOnBindEvents.mockImplementation(() => {})
+
+    const HasMany = new HasManyClass(element)
+
+    const MockSortableArgument = {
+      handle: '.handle',
+      animation: 150,
+      ghostClass: 'sortable-placeholder',
+      dragClass: 'sortable-drag',
+      onUpdate: expect.any(Function)
+    }
+
+    expect(Sortable).toHaveBeenCalledTimes(1)
+    expect(Sortable).toHaveBeenCalledWith(
+      document.querySelector(HasMany.options.list),
+      MockSortableArgument
+    )
+    const sortable = new Sortable(
+      document.querySelector(HasMany.options.list),
+      MockSortableArgument
+    )
+    expect(HasMany.sortable.toString()).toStrictEqual(sortable.toString())
+  })
+
+  test('recomputePosition changes sortableInput value', () => {
+    const query = 'input[name$="[address]"]'
+    const sortableInput = element.querySelector(query)
+
+    expect(sortableInput.value.length).not.toEqual(0)
+
+    const HasMany = new HasManyClass(element)
+    HasMany._recomputePosition()
+
+    expect(sortableInput.value.length).toEqual(0)
+  })
+
+  test('bindDestroyEvent called with element and change event added', () => {
+    const spyOnBindDestroyEvent = jest.spyOn(
+      HasManyClass.prototype,
+      '_bindDestroyEvent'
+    )
+    const destroyInput = document.querySelector(options.destroyInput)
+    destroyInput.addEventListener = jest.fn()
+
+    new HasManyClass(element) // eslint-disable-line no-new
+
+    expect(spyOnBindDestroyEvent).toHaveBeenCalledTimes(1)
+    expect(spyOnBindDestroyEvent).toHaveBeenCalledWith(destroyInput)
+
+    expect(destroyInput.addEventListener).toHaveBeenCalledTimes(1)
+    expect(destroyInput.addEventListener).toHaveBeenCalledWith(
+      'change',
+      expect.any(Function)
+    )
+  })
+
+  test('bindRemoveEvent called with element and click event added', () => {
+    const spyOnBindRemoveEvent = jest.spyOn(
+      HasManyClass.prototype,
+      '_bindRemoveEvent'
+    )
+    const removeLinks = document.querySelector(options.removeLink)
+    removeLinks.addEventListener = jest.fn()
+
+    new HasManyClass(element) // eslint-disable-line no-new
+
+    expect(spyOnBindRemoveEvent).toHaveBeenCalledTimes(1)
+    expect(spyOnBindRemoveEvent).toHaveBeenCalledWith(removeLinks)
+
+    expect(removeLinks.addEventListener).toHaveBeenCalledTimes(1)
+    expect(removeLinks.addEventListener).toHaveBeenCalledWith(
+      'click',
+      expect.any(Function)
+    )
+  })
+
+  test('bindRemoveEventCallBack', () => {
+    const mockEvent = {
+      preventDefault: () => {},
+      target: document.body.querySelector('fieldset')
+    }
+    const spyOnRecomputePosition = jest.spyOn(
+      HasManyClass.prototype,
+      '_recomputePosition'
+    )
+    const HasMany = new HasManyClass(element)
+    const spyOnDispatch = jest.spyOn(HasMany.element, 'dispatchEvent')
+
+    const fieldSet = mockEvent.target.closest(HasMany.options.item)
+    fieldSet.remove = jest.fn()
+
+    const parent = HasMany.element
+    const removeBeforeEvent = HasMany.events.removeBefore
+    removeBeforeEvent.detail = { fieldSet, parent }
+    const removeAfterEvent = HasMany.events.removeAfter
+    removeAfterEvent.detail = { fieldSet, parent }
+
+    const output = HasMany._bindRemoveEventCallBack(mockEvent)
+
+    expect(spyOnRecomputePosition).toHaveBeenCalledTimes(1)
+    expect(spyOnDispatch).toHaveBeenCalledTimes(2)
+    expect(spyOnDispatch.mock.calls).toMatchObject([
+      [removeBeforeEvent],
+      [removeAfterEvent]
+    ])
+    expect(fieldSet.remove).toHaveBeenCalledTimes(1)
+    expect(output).toBeTruthy()
+  })
+
+  test('bindAddEvent called with correctly element and click event added', () => {
+    const spyOnBindAddEvent = jest.spyOn(
+      HasManyClass.prototype,
+      '_bindAddEvent'
+    )
+
+    const addLinks = document.querySelector(options.addLink)
+    addLinks.addEventListener = jest.fn()
+
+    new HasManyClass(element) // eslint-disable-line no-new
+
+    expect(spyOnBindAddEvent).toHaveBeenCalledTimes(1)
+    expect(spyOnBindAddEvent).toHaveBeenCalledWith(addLinks)
+
+    expect(addLinks.addEventListener).toHaveBeenCalledTimes(1)
+    expect(addLinks.addEventListener).toHaveBeenCalledWith(
+      'click',
+      expect.any(Function)
+    )
+  })
+
+  test('bindAddEventCallBack', () => {
+    const mockEvent = {
+      preventDefault: () => {},
+      target: document.body.querySelector(options.addLink)
+    }
+    const HasMany = new HasManyClass(element)
+    const spyOnDispatchEvent = jest.spyOn(HasMany.element, 'dispatchEvent')
+    const $list = HasMany.element.querySelector(HasMany.options.list)
+    const spyOnListAppendChild = jest.spyOn($list, 'appendChild')
+    const spyOnBindEvents = jest.spyOn(HasMany, '_bindEvents')
+    const spyOnRecomputePosition = jest.spyOn(HasMany, '_recomputePosition')
+    const beforeAdd = HasMany.events.addBefore
+    const parent = HasMany.element
+    const datasetHTML = document.createElement('div')
+
+    const output = HasMany._bindAddEventCallBack(mockEvent)
+
+    expect(spyOnDispatchEvent).toHaveBeenCalledTimes(2)
+    expect(spyOnDispatchEvent.mock.calls).toMatchObject([
+      [beforeAdd, [parent]],
+      [HasMany.events.addAfter]
+    ])
+
+    expect(spyOnListAppendChild).toHaveBeenCalledTimes(1)
+    expect(spyOnListAppendChild).toHaveBeenCalledWith(datasetHTML)
+    expect(spyOnBindEvents).toHaveBeenCalledTimes(1)
+    expect(spyOnBindEvents).toHaveBeenCalledWith(datasetHTML)
+    expect(spyOnRecomputePosition).toHaveBeenCalledTimes(1)
+    expect(output).toBeTruthy()
+  })
+})
diff --git a/app/javascript/adminterface/lib/has_many.js b/app/javascript/adminterface/lib/has_many.js
index 69fc3394..27e3608f 100644
--- a/app/javascript/adminterface/lib/has_many.js
+++ b/app/javascript/adminterface/lib/has_many.js
@@ -51,54 +51,57 @@ class HasMany {
   }
 
   _bindAddEvent (el) {
-    el.addEventListener('click', (e) => {
-      let beforeAdd
-      const el = e.target
-      const parent = this.element
+    el.addEventListener('click', (e) => this._bindAddEventCallBack(e))
+  }
 
-      e.preventDefault()
-      parent.dispatchEvent(beforeAdd = this.events.addBefore, [parent])
+  _bindAddEventCallBack (e) {
+    let beforeAdd
+    const el = e.target
+    const parent = this.element
+    e.preventDefault()
+    parent.dispatchEvent(beforeAdd = this.events.addBefore, [parent])
 
-      if (!beforeAdd.defaultPrevented) {
-        let index = parent.dataset.hasManyIndex || parent.querySelectorAll(this.options.item).length - 1
-        parent.setAttribute('data-has-many-index', ++index)
+    if (!beforeAdd.defaultPrevented) {
+      let index = parent.dataset.hasManyIndex || parent.querySelectorAll(this.options.item).length - 1
+      parent.setAttribute('data-has-many-index', ++index)
 
-        const regex = new RegExp(el.dataset.placeholder, 'g')
-        const html = el.dataset.html.replaceAll(regex, index)
-        const newNode = document.createElement('div')
-        newNode.innerHTML = html
+      const regex = new RegExp(el.dataset.placeholder, 'g')
+      const html = el.dataset.html.replace(regex, index)
+      const newNode = document.createElement('div')
+      newNode.innerHTML = html
 
-        const fieldset = newNode.firstElementChild
-        const $list = this.element.querySelector(this.options.list)
+      const fieldset = newNode.firstElementChild
+      const $list = this.element.querySelector(this.options.list)
 
-        $list.appendChild(fieldset)
-        this._bindEvents(fieldset)
-        this._recomputePosition()
+      $list.appendChild(fieldset)
+      this._bindEvents(fieldset)
+      this._recomputePosition()
 
-        const addAfterEvent = this.events.addAfter
-        addAfterEvent.detail = { fieldset, parent }
-        return parent.dispatchEvent(this.events.addAfter)
-      }
-    })
+      const addAfterEvent = this.events.addAfter
+      addAfterEvent.detail = { fieldset, parent }
+      return parent.dispatchEvent(this.events.addAfter)
+    }
   }
 
   _bindRemoveEvent (el) {
-    el.addEventListener('click', (e) => {
-      const el = e.target
-      const parent = this.element
-      const fieldset = el.closest(this.options.item)
-      const removeBeforeEvent = this.events.removeBefore
-      const removeAfterEvent = this.events.removeAfter
-
-      e.preventDefault()
-      this._recomputePosition()
+    el.addEventListener('click', (e) => this._bindRemoveEventCallBack(e))
+  }
 
-      removeBeforeEvent.detail = { fieldset, parent }
-      removeAfterEvent.detail = { fieldset, parent }
-      parent.dispatchEvent(removeBeforeEvent)
-      fieldset.remove()
-      return parent.dispatchEvent(removeAfterEvent)
-    })
+  _bindRemoveEventCallBack (e) {
+    const el = e.target
+    const parent = this.element
+    const fieldset = el.closest(this.options.item)
+    const removeBeforeEvent = this.events.removeBefore
+    const removeAfterEvent = this.events.removeAfter
+
+    e.preventDefault()
+    this._recomputePosition()
+
+    removeBeforeEvent.detail = { fieldset, parent }
+    removeAfterEvent.detail = { fieldset, parent }
+    parent.dispatchEvent(removeBeforeEvent)
+    fieldset.remove()
+    return parent.dispatchEvent(removeAfterEvent)
   }
 
   _bindEvents (el) {