chore: fix code coverage for node env changes (testing-library#126)

This fixes code coverage of testing-library#125 by extracting helper functions.

There are still few istanbul ignores in code but they are not mine :)

Author: sheerun

.size-snapshot.json

@@ -1,7 +1,7 @@
 {
   "dist/dom-testing-library.umd.js": {
-    "bundled": 146890,
-    "minified": 53947,
-    "gzipped": 15849
+    "bundled": 146354,
+    "minified": 53637,
+    "gzipped": 15842
   }
 }

src/__tests__/helpers.js

@@ -0,0 +1,40 @@
+import {getDocument, newMutationObserver} from '../helpers'
+
+describe('getDocument', () => {
+  if (typeof document === 'undefined') {
+    test('throws an error if window does not exist', () => {
+      expect(() => getDocument()).toThrowError(
+        /Could not find default container/,
+      )
+    })
+  } else {
+    test('returns global document if exists', () => {
+      expect(getDocument()).toBe(document)
+    })
+  }
+})
+
+class DummyClass {
+  constructor(args) {
+    this.args = args
+  }
+}
+
+describe('newMutationObserver', () => {
+  if (typeof window === 'undefined') {
+    it('instantiates mock MutationObserver if not availble on window', () => {
+      expect(newMutationObserver(() => {}).observe).toBeDefined()
+    })
+  } else {
+    it('instantiates from global MutationObserver if available', () => {
+      const oldMutationObserver = window.MutationObserver
+      window.MutationObserver = DummyClass
+
+      try {
+        expect(newMutationObserver('foobar').args).toEqual('foobar')
+      } finally {
+        window.MutationObserver = oldMutationObserver
+      }
+    })
+  }
+})

src/helpers.js

@@ -0,0 +1,20 @@
+import MutationObserver from '@sheerun/mutationobserver-shim'
+
+function newMutationObserver(onMutation) {
+  const MutationObserverConstructor =
+    typeof window !== 'undefined' &&
+    typeof window.MutationObserver !== 'undefined'
+      ? window.MutationObserver
+      : MutationObserver
+
+  return new MutationObserverConstructor(onMutation)
+}
+
+function getDocument() {
+  if (typeof window === 'undefined') {
+    throw new Error('Could not find default container')
+  }
+  return window.document
+}
+
+export {getDocument, newMutationObserver}

src/wait-for-dom-change.js

@@ -1,4 +1,4 @@
-import MutationObserver from '@sheerun/mutationobserver-shim'
+import {newMutationObserver, getDocument} from './helpers'
 
 function waitForDomChange({
   container = getDocument(),
@@ -12,13 +12,7 @@ function waitForDomChange({
 } = {}) {
   return new Promise((resolve, reject) => {
     const timer = setTimeout(onTimeout, timeout)
-    /* istanbul ignore next */
-    const MutationObserverConstructor =
-      typeof window !== 'undefined' &&
-      typeof window.MutationObserver !== 'undefined'
-        ? window.MutationObserver
-        : MutationObserver
-    const observer = new MutationObserverConstructor(onMutation)
+    const observer = newMutationObserver(onMutation)
     observer.observe(container, mutationObserverOptions)
 
     function onDone(error, result) {
@@ -39,12 +33,4 @@ function waitForDomChange({
   })
 }
 
-function getDocument() {
-  /* istanbul ignore if */
-  if (typeof window === 'undefined') {
-    throw new Error('Could not find default container')
-  }
-  return window.document
-}
-
 export {waitForDomChange}

src/wait-for-element.js

@@ -1,4 +1,4 @@
-import MutationObserver from '@sheerun/mutationobserver-shim'
+import {newMutationObserver, getDocument} from './helpers'
 
 function waitForElement(
   callback,
@@ -19,13 +19,7 @@ function waitForElement(
     }
     let lastError
     const timer = setTimeout(onTimeout, timeout)
-    /* istanbul ignore next */
-    const MutationObserverConstructor =
-      typeof window !== 'undefined' &&
-      typeof window.MutationObserver !== 'undefined'
-        ? window.MutationObserver
-        : MutationObserver
-    const observer = new MutationObserverConstructor(onMutation)
+    const observer = newMutationObserver(onMutation)
     observer.observe(container, mutationObserverOptions)
     function onDone(error, result) {
       clearTimeout(timer)
@@ -56,12 +50,4 @@ function waitForElement(
   })
 }
 
-function getDocument() {
-  /* istanbul ignore if */
-  if (typeof window === 'undefined') {
-    throw new Error('Could not find default container')
-  }
-  return window.document
-}
-
 export {waitForElement}