add test for dropIndexIfExists and not existing index

test/helpers/dropIndexIfExists/withNotExistingIndex.test.js

@@ -0,0 +1,45 @@
+'use strict';
+
+const testUtils = require('../../utils');
+const helpers = require('../../../lib/helpers');
+
+const test = testUtils.test;
+let adapter;
+
+test('setup', (assert) => {
+	adapter = testUtils.createAdapter();
+
+	return Promise.resolve()
+		.then(() => adapter.connect())
+		.then(() => adapter.collection.dropIndexes());
+});
+
+test(
+	'helpers dropIndexIfExists with existing index',
+	(assert) => {
+		return Promise.resolve()
+			.then(() => {
+				return adapter.helpers.dropIndexIfExists(
+					adapter.collection,
+					{first: 1, second: -1}
+				);
+			})
+			.then(() => adapter.collection.indexes())
+			.then((indexes) => {
+				assert.equal(
+					indexes.length,
+					1,
+					'should leave only one index'
+				);
+				assert.deepEqual(
+					indexes[0].key,
+					{_id: 1},
+					'should leave only one index: _id'
+				);
+			});
+	}
+);
+
+test('teardown', (assert) => {
+	return adapter.disconnect();
+});