Update docs

test/utils/Calldata.test.js

@@ -0,0 +1,22 @@
+const { ethers } = require('hardhat');
+const { expect } = require('chai');
+const { loadFixture } = require('@nomicfoundation/hardhat-network-helpers');
+
+async function fixture() {
+  const mock = await ethers.deployContract('$Calldata');
+  return { mock };
+}
+
+describe('Calldata utilities', function () {
+  beforeEach(async function () {
+    Object.assign(this, await loadFixture(fixture));
+  });
+
+  it('emptyBytes', async function () {
+    await expect(this.mock.$emptyBytes()).to.eventually.equal('0x');
+  });
+
+  it('emptyString', async function () {
+    await expect(this.mock.$emptyString()).to.eventually.equal('');
+  });
+});