Add test to iter reduce

Signed-off-by: Panu Horsmalahti <phorsmalahti@mirantis.com>

src/common/utils/__tests__/iter.test.ts

@@ -0,0 +1,34 @@
+/**
+ * Copyright (c) 2021 OpenLens Authors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to
+ * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+ * the Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+ * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+import { reduce } from "../iter";
+
+describe("iter", () => {
+  describe("reduce", () => {
+    it("can reduce a value", () => {
+      expect(reduce([1, 2, 3], (acc: number[], current: number) => [current, ...acc], [0])).toEqual([3, 2, 1, 0]);
+    });
+
+    it("can reduce an empty iterable", () => {
+      expect(reduce([], (acc: number[], current: number) => [acc[0] + current], [])).toEqual([]);
+    });
+  });
+});

src/common/utils/iter.ts

@@ -160,6 +160,7 @@ export function find<T>(src: Iterable<T>, match: (i: T) => any): T | undefined {
 /**
  * Iterate over `src` calling `reducer` with the previous produced value and the current
  * yielded value until `src` is exausted. Then return the final value.
+ * @param src The value to iterate over
  * @param reducer A function for producing the next item from an accumilation and the current item
  * @param initial The initial value for the iteration
  */