test: Document EOA account call behavior

These tests assert and document the behavior of empty and eoa accounts
with value when called by external transactions with or without data.

In addition, they assert the gas usage is as expected and only depedent
on the base transaction cost plus calldata cost since no code is
executed.

tests/e2e-evm/test/empty_account.test.ts

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+import hre from "hardhat";
+import { expect } from "chai";
+import { Address, toHex } from "viem";
+import { randomBytes } from "crypto";
+import { whaleAddress } from "./addresses";
+
+// Empty Account describes how transactions behave against an account with
+// with no balance, no code, and no nonce.
+//
+// Accounts without code can be called with any data and value.
+describe("Empty Account", function () {
+  const emptyAddress: Address = toHex(randomBytes(20));
+
+  // The definition of an empty account
+  it("has no balance, no code, and zero nonce", async function () {
+    const publicClient = await hre.viem.getPublicClient();
+
+    const balance = await publicClient.getBalance({ address: emptyAddress });
+    const code = await publicClient.getCode({ address: emptyAddress });
+    const nonce = await publicClient.getTransactionCount({ address: emptyAddress });
+
+    expect(balance).to.equal(0n);
+    expect(code).to.be.undefined;
+    expect(nonce).to.equal(0);
+  });
+
+  // An empty account can receive a 0 value transaction
+  it("can be called with no data or value", async function () {
+    const publicClient = await hre.viem.getPublicClient();
+    const walletClient = await hre.viem.getWalletClient(whaleAddress);
+
+    const txHash = await walletClient.sendTransaction({
+      to: emptyAddress,
+    });
+    const txReceipt = await publicClient.waitForTransactionReceipt({ hash: txHash });
+    const tx = await publicClient.getTransaction({ hash: txHash });
+
+    expect(txReceipt.status).to.equal("success");
+    expect(txReceipt.gasUsed).to.equal(21000n);
+    expect(tx.value).to.equal(0n);
+    expect(tx.to).to.equal(emptyAddress);
+    expect(tx.input).to.equal("0x");
+  });
+
+  // An empty account can receive a call with any data payload
+  it("can be called with data", async function () {
+    const publicClient = await hre.viem.getPublicClient();
+    const walletClient = await hre.viem.getWalletClient(whaleAddress);
+
+    // 16 bytes with 1 of them zero
+    // 16 * 15 + 4 * 1 = 244 gas
+    const calldata = "0x1eb478108900a0b492ef5dd03921d02d";
+
+    const txHash = await walletClient.sendTransaction({
+      to: emptyAddress,
+      data: calldata,
+    });
+    const txReceipt = await publicClient.waitForTransactionReceipt({ hash: txHash });
+    const tx = await publicClient.getTransaction({ hash: txHash });
+
+    expect(txReceipt.status).to.equal("success");
+    // exact gas -- no memory expansion or op code charges
+    expect(txReceipt.gasUsed).to.equal(21000n + 244n);
+    expect(tx.value).to.equal(0n);
+    expect(tx.to).to.equal(emptyAddress);
+    expect(tx.input).to.equal(calldata);
+  });
+});

tests/e2e-evm/test/eoa_account.test.ts

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+import hre from "hardhat";
+import { expect } from "chai";
+import { Address, toHex } from "viem";
+import { randomBytes } from "crypto";
+import { whaleAddress, userAddress } from "./addresses";
+
+// EOA Account describes how transactions behave against an account with
+// with no code while holding a balance.
+//
+// Accounts without code can be called with any data and value.
+describe("EOA Account", function () {
+  it("has a balance and no code", async function () {
+    const publicClient = await hre.viem.getPublicClient();
+
+    const balance = await publicClient.getBalance({ address: userAddress });
+    const code = await publicClient.getCode({ address: userAddress });
+
+    expect(balance).to.not.equal(0n);
+    expect(code).to.be.undefined;
+  });
+
+  it("can be called with no data or value", async function () {
+    const publicClient = await hre.viem.getPublicClient();
+    const walletClient = await hre.viem.getWalletClient(whaleAddress);
+
+    const txHash = await walletClient.sendTransaction({
+      to: userAddress,
+    });
+    const txReceipt = await publicClient.waitForTransactionReceipt({ hash: txHash });
+    const tx = await publicClient.getTransaction({ hash: txHash });
+
+    expect(txReceipt.status).to.equal("success");
+    expect(txReceipt.gasUsed).to.equal(21000n);
+    expect(tx.value).to.equal(0n);
+    expect(tx.to).to.equal(userAddress);
+    expect(tx.input).to.equal("0x");
+  });
+
+  it("can be called with data", async function () {
+    const publicClient = await hre.viem.getPublicClient();
+    const walletClient = await hre.viem.getWalletClient(whaleAddress);
+
+    // 16 bytes with 1 of them zero
+    // 16 * 15 + 4 * 1 = 244 gas
+    const calldata = "0x1eb478108900a0b492ef5dd03921d02d";
+
+    const txHash = await walletClient.sendTransaction({
+      to: userAddress,
+      data: calldata,
+    });
+    const txReceipt = await publicClient.waitForTransactionReceipt({ hash: txHash });
+    const tx = await publicClient.getTransaction({ hash: txHash });
+
+    expect(txReceipt.status).to.equal("success");
+    // exact gas -- no memory expansion or op code charges
+    expect(txReceipt.gasUsed).to.equal(21000n + 244n);
+    expect(tx.value).to.equal(0n);
+    expect(tx.to).to.equal(userAddress);
+    expect(tx.input).to.equal(calldata);
+  });
+
+  it("can be called with data and value", async function () {
+    const publicClient = await hre.viem.getPublicClient();
+    const walletClient = await hre.viem.getWalletClient(whaleAddress);
+
+    // 4 non-zero bytes
+    // 16 * 4 = 64 gas
+    const calldata = "0x1eb47810";
+
+    const txHash = await walletClient.sendTransaction({
+      to: userAddress,
+      data: calldata,
+    });
+    const txReceipt = await publicClient.waitForTransactionReceipt({ hash: txHash });
+    const tx = await publicClient.getTransaction({ hash: txHash });
+
+    expect(txReceipt.status).to.equal("success");
+    // exact gas -- no memory expansion or op code charges
+    expect(txReceipt.gasUsed).to.equal(21000n + 64n);
+    expect(tx.value).to.equal(0n);
+    expect(tx.to).to.equal(userAddress);
+    expect(tx.input).to.equal(calldata);
+  });
+});