Add some technical tests

Signed-off-by: Sebastian Malton <sebastian@malton.name>

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

@@ -3,7 +3,7 @@
  * Licensed under MIT License. See LICENSE in root directory for more information.
  */
 
-import { join, nth, reduce } from "../iter";
+import { join, nth, reduce, concat } from "../iter";
 
 describe("iter", () => {
   describe("reduce", () => {
@@ -39,4 +39,30 @@ describe("iter", () => {
       expect(nth(["a", "b"], 0)).toBe("a");
     });
   });
+
+  describe("concat", () => {
+    it("should yield undefined for empty args", () => {
+      const iter = concat();
+
+      expect(iter.next()).toEqual({ done: true });
+    });
+
+    it("should yield undefined for only empty args", () => {
+      const iter = concat([].values(), [].values(), [].values(), [].values());
+
+      expect(iter.next()).toEqual({ done: true });
+    });
+
+    it("should yield all of the first and then all of the second", () => {
+      const iter = concat([1, 2, 3].values(), [4, 5, 6].values());
+
+      expect(iter.next()).toEqual({ done: false, value: 1 });
+      expect(iter.next()).toEqual({ done: false, value: 2 });
+      expect(iter.next()).toEqual({ done: false, value: 3 });
+      expect(iter.next()).toEqual({ done: false, value: 4 });
+      expect(iter.next()).toEqual({ done: false, value: 5 });
+      expect(iter.next()).toEqual({ done: false, value: 6 });
+      expect(iter.next()).toEqual({ done: true });
+    });
+  });
 });

src/common/utils/iter.ts

@@ -239,12 +239,10 @@ export function every<T>(src: Iterable<T>, fn: (val: T) => any): boolean {
   return true;
 }
 
-export function* concat<T>(src1: IterableIterator<T>, src2: IterableIterator<T>): IterableIterator<T> {
+export function* concat<T>(...sources: IterableIterator<T>[]): IterableIterator<T> {
-  for (const val of src1) {
+  for (const source of sources) {
-    yield val;
+    for (const val of source) {
-  }
+      yield val;
-
+    }
-  for (const val of src2) {
-    yield val;
   }
 }