jsutils: add test for Path functions (#2478)

Co-authored-by: Ivan Goncharov <ivan.goncharov.ua@gmail.com>

src/jsutils/__tests__/Path-test.ts

@@ -0,0 +1,36 @@
+import { expect } from 'chai';
+import { describe, it } from 'mocha';
+
+import { addPath, pathToArray } from '../Path';
+
+describe('Path', () => {
+  it('can create a Path', () => {
+    const first = addPath(undefined, 1, 'First');
+
+    expect(first).to.deep.equal({
+      prev: undefined,
+      key: 1,
+      typename: 'First',
+    });
+  });
+
+  it('can add a new key to an existing Path', () => {
+    const first = addPath(undefined, 1, 'First');
+    const second = addPath(first, 'two', 'Second');
+
+    expect(second).to.deep.equal({
+      prev: first,
+      key: 'two',
+      typename: 'Second',
+    });
+  });
+
+  it('can convert a Path to an array of its keys', () => {
+    const root = addPath(undefined, 0, 'Root');
+    const first = addPath(root, 'one', 'First');
+    const second = addPath(first, 2, 'Second');
+
+    const path = pathToArray(second);
+    expect(path).to.deep.equal([0, 'one', 2]);
+  });
+});