feat(exists): add exists method

Author: eddyerburgh

docs/en/api/wrapper/exists.md

@@ -0,0 +1,21 @@
+# exists()
+
+- **Returns:** `{boolean}`
+
+- **Usage:**
+
+Assert `Wrapper` or `WrapperArray` exists.
+
+Returns false if called on an empty `Wrapper` or `WrapperArray`.
+
+```js
+import { mount } from 'vue-test-utils'
+import { expect } from 'chai'
+import Foo from './Foo.vue'
+
+const wrapper = mount(Foo)
+expect(wrapper.exists()).to.equal(true)
+expect(wrapper.find('does-not-exist').exists()).to.equal(false)
+expect(wrapper.findAll('div').exists()).to.equal(true)
+expect(wrapper.findAll('does-not-exist').exists()).to.equal(false)
+```

flow/wrapper.js

@@ -6,6 +6,7 @@ import type WrapperArray from '~src/WrapperArray'
 declare interface BaseWrapper { // eslint-disable-line no-undef
     at(index: number): Wrapper | void,
     contains(selector: String | Component): boolean | void,
+    exists(): boolean,
     hasAttribute(attribute: string, value: string): boolean | void,
     hasClass(className: string): boolean | void,
     hasProp(prop: string, value: string): boolean | void,

src/wrappers/error-wrapper.js

@@ -16,6 +16,10 @@ export default class ErrorWrapper implements BaseWrapper {
     throwError(`find did not return ${this.selector}, cannot call contains() on empty Wrapper`)
   }
 
+  exists (): boolean {
+    return false
+  }
+
   hasAttribute (): void {
     throwError(`find did not return ${this.selector}, cannot call hasAttribute() on empty Wrapper`)
   }

src/wrappers/wrapper-array.js

@@ -26,6 +26,10 @@ export default class WrapperArray implements BaseWrapper {
     return this.wrappers.every(wrapper => wrapper.contains(selector))
   }
 
+  exists (): boolean {
+    return this.wrappers.length > 0
+  }
+
   hasAttribute (attribute: string, value: string): boolean {
     this.throwErrorIfWrappersIsEmpty('hasAttribute')
 

src/wrappers/wrapper.js

@@ -47,6 +47,13 @@ export default class Wrapper implements BaseWrapper {
     return false
   }
 
+  /**
+   * Utility to check wrapper exists. Returns true as Wrapper always exists
+   */
+  exists (): boolean {
+    return true
+  }
+
   /**
    * Checks if wrapper has an attribute with matching value
    */

test/integration/specs/mount/Wrapper/exists.spec.js

@@ -0,0 +1,16 @@
+import { compileToFunctions } from 'vue-template-compiler'
+import mount from '~src/mount'
+
+describe('exists', () => {
+  it('returns true if called on Wrapper', () => {
+    const compiled = compileToFunctions('<div />')
+    const wrapper = mount(compiled)
+    expect(wrapper.exists()).to.equal(true)
+  })
+
+  it('returns false if called on an ErrorWrapper', () => {
+    const compiled = compileToFunctions('<div />')
+    const wrapper = mount(compiled)
+    expect(wrapper.find('does-not-exist').exists()).to.equal(false)
+  })
+})

test/unit/specs/wrappers/wrapper-array.spec.js

@@ -48,6 +48,16 @@ describe('WrapperArray', () => {
     expect(wrapperArray.contains()).to.equal(false)
   })
 
+  it('exists returns true if length is greater then 0', () => {
+    const wrapperArray = new WrapperArray([{}])
+    expect(wrapperArray.exists()).to.equal(true)
+  })
+
+  it('exists returns false if length is 0', () => {
+    const wrapperArray = new WrapperArray([])
+    expect(wrapperArray.exists()).to.equal(false)
+  })
+
   it('hasAttribute returns true if every wrapper.hasAttribute() returns true', () => {
     const attribute = 'attribute'
     const value = 'value'