Define Incorrect Behavior of haveInvoiceItems

app/models/inventory-batch.js

@@ -7,7 +7,7 @@ import Ember from 'ember';
 export default AbstractModel.extend({
   haveInvoiceItems() {
     let invoiceItems = this.get('invoiceItems');
-    return (Ember.isEmpty(invoiceItems));
+    return !Ember.isEmpty(invoiceItems);
   },
 
   validations: {

tests/unit/models/inventory-batch-test.js

@@ -0,0 +1,22 @@
+import { moduleForModel, test } from 'ember-qunit';
+
+moduleForModel('inventory-batch', 'Unit | Model | inventory-batch', {
+  needs: [
+    'ember-validations@validator:local/presence',
+    'ember-validations@validator:local/numericality'
+  ]
+});
+
+test('haveInvoiceItems', function(assert) {
+  let inventoryBatch = this.subject({
+    invoiceItems: ['test']
+  });
+
+  assert.strictEqual(inventoryBatch.haveInvoiceItems(), true);
+});
+
+test('haveInvoiceItems false', function(assert) {
+  let inventoryBatch = this.subject();
+
+  assert.strictEqual(inventoryBatch.haveInvoiceItems(), false);
+});