add HintKeyProducer

test/content/hint-key-producer.test.js

@@ -0,0 +1,25 @@
+import { expect } from "chai";
+import HintKeyProducer from '../../src/content/hint-key-producer';
+
+describe('HintKeyProducer class', () => {
+  describe('#constructor', () => {
+    it('throws an exception on empty charset', () => {
+      expect(() => new HintKeyProducer([])).to.throw(TypeError);
+    });
+  });
+
+  describe('#produce', () => {
+    it('produce incremented keys', () => {
+      let charset = 'abc';
+      let sequences = [
+        'a', 'b', 'c',
+        'aa', 'ab', 'ac', 'ba', 'bb', 'bc', 'ca', 'cb', 'cc',
+        'aaa', 'aab', 'aac', 'aba']
+
+      let producer = new HintKeyProducer(charset);
+      for (let i = 0; i < sequences.length; ++i) {
+        expect(producer.produce()).to.equal(sequences[i]);
+      }
+    });
+  });
+});