Debugging Functional Tests in Bitcoin: Fixing “JSONRPCException: method not found”

Bitcoin functional tests are essential to ensure the correctness of blockchain and wallet implementations. However, sometimes these tests fail with a cryptic error message, JSONRPCException: method not found (-32601). In this article, we will go over three common functional tests that failed in your test_runner.py file and provide solutions to resolve the issue.

Test 1: Test_Coins

The Test_Coins test checks whether coins were created correctly. It expects a call to a specific method on the blockchain with the correct input parameters.

Solution

Make sure that the createCoin method is implemented in the blockchain.py file and that the necessary arguments (coinName, amount, pubkey) have been passed to the expected method call:

blockchain.py
def createCoin(coinName, amount, pubkey):

...

Verify that this implementation matches the test expectations.

Test 2: Test_CoinsGetTransaction

The Test_CoinsGetTransaction test verifies whether a coin transaction is retrieved successfully. It expects a specific method call on the blockchain with the correct input parameters.

Solution

Verify that the getTransaction method in the blockchain.py file matches the expected function signature:

blockchain.py
def getTransaction(id):

...

Verify that this implementation meets the test expectations. If the solution does not resolve the issue, ensure that the method call is correct and passes the required arguments.

Test 3: Test_Bytes

The Test_Bytes test verifies whether bytes are correctly transmitted over JSON-RPC. It expects a call to the specific method on the blockchain with the correct input parameters.

Solution

Verify that the sendBytes method in the blockchain.py file matches the expected function signature:

blockchain.py
def sendBytes(id, data):

...

Make sure this implementation meets the expectations of the test. If the solution does not resolve the issue, verify that the method call is correct and passes the necessary arguments.

Additional Tips

• Make sure all tests are running before attempting to debug the test_runner.py file.

• Use a debugger or print statements to inspect variables and function calls during test execution.

• Consider adding more error checking and logging in your tests to help diagnose issues.

By following these steps, you should be able to identify and fix the issue causing “JSONRPCException: Method not found” errors in your Bitcoin functional tests.