Writing Effective Unit Tests

The mission of the ckb-js-vm project is to enable developers to write on-chain scripts using a single language: TypeScript. In the previous chapter, we learned how to write on-chain scripts in TypeScript. This chapter will demonstrate how you can also write unit tests in TypeScript, allowing you to use just one language for your entire development workflow.

ckb-testtool

While Rust developers have been using ckb-testtool for testing, we now have a TypeScript version of ckb-testtool available. This tool leverages two important components:

1. ccc - A transaction assembler written in TypeScript
2. ckb-debugger - A debugger and execution environment

The workflow is straightforward:

• Use ccc to assemble transactions in TypeScript, outputting them in JSON format
• Use ckb-debugger to execute and validate these transactions
• Write assertions to verify the expected behavior

This combination provides a complete unit testing framework for CKB scripts written in TypeScript.

Examples

describe("example", () => {
  test("alwaysSuccess", () => {
    const resource = Resource.default();
    const tx = Transaction.default();

    // deploy a cell with risc-v binary, return a script.
    const lockScript = resource.deployCell(
      hexFrom(readFileSync(DEFAULT_SCRIPT_ALWAYS_SUCCESS)),
      tx,
      false,
    );
    // update args
    lockScript.args = "0xEEFF";

    // mock a input cell with the created script as lock script
    const inputCell = resource.mockCell(lockScript);

    // add input cell to the transaction
    tx.inputs.push(Resource.createCellInput(inputCell));
    // add output cell to the transaction
    tx.outputs.push(Resource.createCellOutput(lockScript));
    // add output data to the transaction
    tx.outputsData.push(hexFrom("0x"));

    // verify the transaction
    const verifier = Verifier.from(resource, tx);
    verifier.verifySuccess();
  });

  test("alwaysFailure", () => {
    const resource = Resource.default();
    const tx = Transaction.default();

    const lockScript = resource.deployCell(
      hexFrom(readFileSync(DEFAULT_SCRIPT_ALWAYS_FAILURE)),
      tx,
      false,
    );
    const inputCell = resource.mockCell(lockScript);
    tx.inputs.push(Resource.createCellInput(inputCell));

    const verifier = Verifier.from(resource, tx);
    verifier.verifyFailure();
    verifier.verifyFailure(-1);
  });
});

In the example above, we're testing on-chain script with two test cases:

1. A test case which succeeds
2. A test case which fails

This pattern allows you to verify both the positive and negative cases for your script's validation logic, ensuring robust behavior in all scenarios.

Pre-compiled Test Binaries

To simplify testing, the ckb-js-vm project provides several pre-compiled binaries that you can use in your test cases:

1. Always Success Script - A script that always returns success (exit code 0)

   • Access via DEFAULT_SCRIPT_ALWAYS_SUCCESS

2. Always Failure Script - A script that always returns failure (exit code -1)

   • Access via DEFAULT_SCRIPT_ALWAYS_FAILURE

3. ckb-js-vm Script - The main ckb-js-vm runtime for testing TypeScript scripts

   • Access via DEFAULT_SCRIPT_CKB_JS_VM

These binaries can be imported directly in your tests without needing to compile them yourself, making it easier to create test fixtures and validation scenarios.

Example usage:

// Import the binary
const alwaysSuccessScript = hexFrom(readFileSync(DEFAULT_SCRIPT_ALWAYS_SUCCESS));

// Deploy it in your test
const lockScript = resource.deployCell(alwaysSuccessScript, tx, false);

⚠️ SECURITY WARNING: These pre-compiled binaries are intended for testing purposes only. Never deploy them in a production environment. For production use, always compile your scripts from source code to ensure security and integrity.