reject with useful reason, rather then undefined when a scheduled fet…

…ch fails to contain an expected record.

addon/-private/system/store.js

@@ -906,10 +906,11 @@ Store = Service.extend({
 
     function rejectInternalModels(internalModels, error) {
       for (let i = 0, l = internalModels.length; i < l; i++) {
-        let pair = seeking[internalModels[i].id];
+        let internalModel = internalModels[i];
+        let pair = seeking[internalModel.id];
 
         if (pair) {
-          pair.resolver.reject(error);
+          pair.resolver.reject(error || new Error(`Expected: '${internalModel}' to be present in the adapter provided payload, but it was not found.`));
         }
       }
     }

tests/unit/store/adapter-interop-test.js

@@ -818,22 +818,25 @@ test("the promise returned by `_scheduleFetch`, when it rejects, does not depend
     }
   });
 
-  var store = createStore({
-    adapter: adapter,
+  let store = createStore({
+    adapter: Adapter,
     test: Person
   });
 
-  run(function () {
-    var davidPromise = store.findRecord('test', 'david');
-    var igorPromise = store.findRecord('test', 'igor');
+  return run(() => {
+    let david = store.findRecord('test', 'david');
+    let igor = store.findRecord('test', 'igor');
+    let wait = [];
 
-    igorPromise.then(null, assert.wait(function () {
-      assert.equal(davidResolved, false, "Igor did not need to wait for David");
+    wait.push(igor.catch(() => {
+      assert.equal(davidResolved, false, 'Igor did not need to wait for David');
     }));
 
-    davidPromise.then(assert.wait(function () {
-      assert.equal(davidResolved, true, "David resolved");
+    wait.push(david.then(() => {
+      assert.equal(davidResolved, true, 'David resolved');
     }));
+
+    return Ember.RSVP.Promise.all(wait);
   });
 });