Added hook test

Author: erikras

src/useFieldArray.test.js

@@ -0,0 +1,61 @@
+import React from 'react'
+import { render, cleanup } from 'react-testing-library'
+import 'jest-dom/extend-expect'
+import arrayMutators from 'final-form-arrays'
+import { ErrorBoundary } from './testUtils'
+import { Form } from 'react-final-form'
+import useFieldArray from './useFieldArray'
+
+const onSubmitMock = values => {}
+
+describe('FieldArray', () => {
+  afterEach(cleanup)
+
+  // Most of the functionality of useFieldArray is tested in FieldArray.test.js
+  // This file is only for testing its use as a hook in other components
+
+  it('should warn if not used inside a form', () => {
+    jest.spyOn(console, 'error').mockImplementation(() => {})
+    const errorSpy = jest.fn()
+    const MyFieldComponent = () => {
+      useFieldArray('name')
+      return <div />
+    }
+    render(
+      <ErrorBoundary spy={errorSpy}>
+        <MyFieldComponent />
+      </ErrorBoundary>
+    )
+    expect(errorSpy).toHaveBeenCalled()
+    expect(errorSpy).toHaveBeenCalledTimes(1)
+    expect(errorSpy.mock.calls[0][0].message).toBe(
+      'useFieldArray must be used inside of a <Form> component'
+    )
+    console.error.mockRestore()
+  })
+
+  it('should track field array state', () => {
+    const spy = jest.fn()
+    const MyFieldArray = () => {
+      spy(useFieldArray('names'))
+      return null
+    }
+    render(
+      <Form onSubmit={onSubmitMock} mutators={arrayMutators} subscription={{}}>
+        {() => (
+          <form>
+            <MyFieldArray />
+          </form>
+        )}
+      </Form>
+    )
+    expect(spy).toHaveBeenCalled()
+    expect(spy).toHaveBeenCalledTimes(1)
+    expect(spy.mock.calls[0][0].fields.length).toBe(0)
+
+    spy.mock.calls[0][0].fields.push('bob')
+
+    expect(spy).toHaveBeenCalledTimes(2)
+    expect(spy.mock.calls[1][0].fields.length).toBe(1)
+  })
+})