Avoid changing existing tests

Rewrites the tests to preserve the original tests and adds new tests to
document the added functionality.

Author: jklina

test/test.js

@@ -13,13 +13,24 @@ describe('session-resume', function () {
 
   describe('restoreResumableFields', function () {
     it('restores fields values from session storage', function () {
+      sessionStorage.setItem('session-resume:test-persist', JSON.stringify([['my-first-field', 'test2']]))
+      restoreResumableFields('test-persist')
+
+      assert.equal(document.querySelector('#my-first-field').value, 'test2')
+      assert.equal(document.querySelector('#my-second-field').value, 'second-field-value')
+    })
+
+    it('leaves unrestored values in session storage', function () {
       sessionStorage.setItem(
         'session-resume:test-persist',
         JSON.stringify([
           ['my-first-field', 'test2'],
           ['non-existant-field', 'test3']
         ])
       )
+      document.querySelector('#my-first-field').value = 'first-field-value'
+      document.querySelector('#my-second-field').value = 'second-field-value'
+
       restoreResumableFields('test-persist')
 
       assert.equal(document.querySelector('#my-first-field').value, 'test2')
@@ -67,13 +78,18 @@ describe('session-resume', function () {
 
   describe('persistResumableFields', function () {
     it('persist fields values to session storage', function () {
-      sessionStorage.setItem(
-        'session-resume:test-persist',
-        JSON.stringify([
-          ['my-first-field', 'old data'],
-          ['non-existant-field', 'test3']
-        ])
-      )
+      document.querySelector('#my-first-field').value = 'test1'
+      document.querySelector('#my-second-field').value = 'test2'
+      persistResumableFields('test-persist')
+
+      assert.deepEqual(JSON.parse(sessionStorage.getItem('session-resume:test-persist')), [
+        ['my-first-field', 'test1'],
+        ['my-second-field', 'test2']
+      ])
+    })
+
+    it('holds onto existing values in the store', function () {
+      sessionStorage.setItem('session-resume:test-persist', JSON.stringify([['non-existant-field', 'test3']]))
       document.querySelector('#my-first-field').value = 'test1'
       document.querySelector('#my-second-field').value = 'test2'
 
@@ -85,5 +101,18 @@ describe('session-resume', function () {
         ['non-existant-field', 'test3']
       ])
     })
+
+    it('replaces old values with the latest field values', function () {
+      sessionStorage.setItem('session-resume:test-persist', JSON.stringify([['my-first-field', 'old data']]))
+      document.querySelector('#my-first-field').value = 'test1'
+      document.querySelector('#my-second-field').value = 'test2'
+
+      persistResumableFields('test-persist')
+
+      assert.deepEqual(JSON.parse(sessionStorage.getItem('session-resume:test-persist')), [
+        ['my-first-field', 'test1'],
+        ['my-second-field', 'test2']
+      ])
+    })
   })
 })