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Testing Smart Contracts

This guide explains how to effectively test smart contracts on OP_NET using the Unit Test Framework. It covers deploying contracts, interacting with them, and verifying their state changes.

Deploying Contracts in Tests​

1. Instantiating Contract Instances​

Create a contract instance and configure it with its deployment parameters.

import { OP_20 } from "@btc-vision/unit-test-framework";

const contract = new OP_20({
  file: "MyToken", // Contract file name (it should be in the bytecode folder as MyToken.wasm for example)
  deployer: Blockchain.generateRandomAddress(), // Deployer address
  address: Blockchain.generateRandomAddress(), // Contract address
  decimals: 18, // Number of decimals
  gasLimit: 100_000_000_000n, // (Optional) Gas limit, default is 100_000_000_000n
});

2. Registering Contracts with the Blockchain​

Register the contract instance with the blockchain using Blockchain.register.

import { Blockchain } from "@btc-vision/unit-test-framework";

Blockchain.register(contract); // Register the contract with the blockchain

3. Initializing Contracts with Parameters (Calldata)​

You can initialize contracts with specific parameters, typically passed as calldata.

await contract.init(); // Initialize contract
await contract.deployContract(); // Deploy the contract on the blockchain

Interacting with Contracts​

1. Calling Contract Methods​

Call contract methods by invoking the respective functions on the contract instance.

const receiverAddress = Blockchain.generateRandomAddress();
await contract.mint(receiverAddress, 1000); // Mint tokens to a specific address

2. Passing Parameters and Handling Return Values​

Pass arguments to contract methods and handle the return values.

const balance = await contract.balanceOf(receiverAddress);
Blockchain.log(`Balance: ${balance}`);

Testing Contract State Changes​

1. Verifying Storage Changes and State Variables​

Ensure that the contract's state changes as expected after a method call.

const testAddress = Blockchain.generateRandomAddress();
await contract.mint(testAddress, 1000);
const newBalance = await contract.balanceOfNoDecimals(testAddress);

Assert.expect(newBalance).toEqual(1000); // Verify the balance was updated

Example Test: Deploying and Interacting with a Contract​

import { Address } from "@btc-vision/transaction";
import {
  Assert,
  Blockchain,
  OP_20,
  opnet,
  OPNetUnit,
} from "@btc-vision/unit-test-framework";

const rndAddress = Blockchain.generateRandomAddress();
const receiver: Address = Blockchain.generateRandomAddress();

await opnet("Contract Interaction Tests", async (vm: OPNetUnit) => {
  Blockchain.msgSender = receiver;
  Blockchain.txOrigin = receiver;

  vm.beforeEach(async () => {
    await Blockchain.init();
  });

  vm.afterAll(() => {
    Blockchain.dispose();
  });

  const contract = new OP_20({
    file: "MyToken",
    deployer: Blockchain.txOrigin,
    address: rndAddress,
    decimals: 18,
    gasLimit: 100_000_000_000n,
  });

  Blockchain.register(contract);

  await vm.it("should mint tokens and update balance", async () => {
    const testAddress = Blockchain.generateRandomAddress();
    await contract.mint(testAddress, 1000);

    const balance = await contract.balanceOfNoDecimals(testAddress);
    Assert.expect(balance).toEqual(1000);
  });
});

Best Practices​

  • Utilize vm.beforeEach and vm.afterEach to reset states between tests.
  • Use Blockchain.log to track contract interactions during tests.
  • Use assertions to verify storage and state changes after each operation.
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