Unit Code Testing Strategy for Iterators

[jonmchan]

I'm writing a smart contract in typescript. After generating the project from IBM Blockchain Platform vscode plugin, I noticed the general unit code testing strategy was to mock the stubs such as:

ctx.stub.getState.withArgs('1010').resolves(Buffer.from('{"id":"1010","data":{}}'));

I wanted to test my function that called the getHistoryForKey function but ran into some major issues with the iterator. I created a solution but would like some feedback on it. Would this be the most optimal way to stub/mock hyperledger fabric functions that return iterators?

import { Context } from 'fabric-contract-api';
import { ChaincodeStub, ClientIdentity, Iterators } from 'fabric-shim';
import { HistoryQueryIterator } from 'fabric-shim/lib/iterators';
import { ChaincodeMessageHandler } from 'fabric-shim/lib/handler';

chai.should();
chai.use(chaiAsPromised);
chai.use(sinonChai);

// test context updated to match fabric-contract-api version 2.4.1
class TestContext implements Context {
  public stub: sinon.SinonStubbedInstance<ChaincodeStub> = sinon.createStubInstance(ChaincodeStub);
  public clientIdentity: sinon.SinonStubbedInstance<ClientIdentity> = sinon.createStubInstance(ClientIdentity);
  public logging = {
    getLogger: sinon.stub().returns(sinon.createStubInstance(winston.createLogger().constructor)),
    setLevel: sinon.stub(),
  };
}

describe('MyContract', () => {

  let ctx: TestContext;
  let mockHandler: ChaincodeMessageHandler;
  let mockResponse: { results: any, hasMore: boolean };
  let sandbox;

  beforeEach(() => {
    ...

    sandbox = sinon.createSandbox();
    mockHandler = sandbox.createStubInstance(ChaincodeMessageHandler);

    // we're not actually processing the results, so just fill the results array with the number of items you want to simulate returning in history
    mockResponse = {results: [1,2,3,4,5], hasMore: false};

    const iterator = new HistoryQueryIterator(mockHandler, 'TestChannelID','txId',mockResponse);

    const getResultsFromBytesStub = sinon.stub(iterator, '_getResultFromBytes');

    // mocking out the actual responses returned with each iteration
    getResultsFromBytesStub.onCall(0).returns({ value: Buffer.from('{"id":"1000","data":{"value": 1}}')});
    getResultsFromBytesStub.onCall(1).returns({ value: Buffer.from('{"id":"1000","data":{"value": 2}}')});
    getResultsFromBytesStub.onCall(2).returns({ value: Buffer.from('{"id":"1000","data":{"value": 3}}')});
    getResultsFromBytesStub.onCall(3).returns({ value: Buffer.from('{"id":"1000","data":{"value": 4}}')});
    getResultsFromBytesStub.onCall(4).returns({ value: Buffer.from('{"id":"1000","data":{"value": 5}}')});


    ctx.stub.getHistoryForKey.withArgs('1000').resolves(iterator);
  });

...

https://stackoverflow.com/questions/71317787/how-to-generate-mocked-object-for-gethistoryforkey-method/71359764#71359764

@mbwhite @jt-nti - your thoughts?

[rajat-dlt]

@jonmchan ,
I had similar questions. There's no official documentation on how to write test cases generally for a chaincode.

@bestbeforetoday could you help with this ?