Fail focus tests quickly and clearly if document isn't focused

spec/text-editor-component-spec.js

@@ -186,6 +186,8 @@ describe('TextEditorComponent', () => {
 
   describe('focus', () => {
     it('focuses the hidden input element and adds the is-focused class when focused', async () => {
+      assertDocumentFocused()
+
       const {component, element, editor} = buildComponent()
       const {hiddenInput} = component.refs
 
@@ -206,6 +208,8 @@ describe('TextEditorComponent', () => {
     })
 
     it('updates the component when the hidden input is focused directly', async () => {
+      assertDocumentFocused()
+
       const {component, element, editor} = buildComponent()
       const {hiddenInput} = component.refs
       expect(element.classList.contains('is-focused')).toBe(false)
@@ -217,6 +221,8 @@ describe('TextEditorComponent', () => {
     })
 
     it('gracefully handles a focus event that occurs prior to the attachedCallback of the element', () => {
+      assertDocumentFocused()
+
       const {component, element, editor} = buildComponent({attach: false})
       const parent = document.createElement('text-editor-component-test-element')
       parent.appendChild(element)
@@ -361,3 +367,9 @@ function textNodesForScreenRow (component, row) {
   const screenLine = component.getModel().screenLineForScreenRow(row)
   return component.textNodesByScreenLineId.get(screenLine.id)
 }
+
+function assertDocumentFocused () {
+  if (!document.hasFocus()) {
+    throw new Error('The document needs to be focused to run this test')
+  }
+}