add tests

.gitignore

@@ -1,9 +1,10 @@
-# IDE
-.idea
-.vscode
-
-# Node
-node_modules
-
-# MacOS
-.DS_Store
+# IDE
+.idea
+.vscode
+
+# Node
+node_modules
+
+# MacOS
+.DS_Store
+config.bat

src/isIsogram.test.js

@@ -1,9 +1,29 @@
-'use strict';
+"use strict";
 
-describe('isIsogram', () => {
-  const { isIsogram } = require('./isIsogram');
+describe("isIsogram", () => {
+  const { isIsogram } = require("./isIsogram");
 
   it(`should be declared`, () => {
     expect(isIsogram).toBeInstanceOf(Function);
   });
+
+  it(`should return true for 'playgrounds'`, () => {
+    expect(isIsogram("playgrounds")).toBe(true);
+  });
+
+  it(`should return false for 'look'`, () => {
+    expect(isIsogram("look")).toBe(false);
+  });
+
+  it(`should return false for 'Adam'`, () => {
+    expect(isIsogram("Adam")).toBe(false);
+  });
+
+  it("should be return  true for empty string", () => {
+    expect(isIsogram("")).toBe(true);
+  });
+
+  it("should be return  false for (Oops) ", () => {
+    expect(isIsogram("Oops")).toBe(false);
+  });
 });