Unit Testing

• create python test files in tests folder.

• filenames must begin with test_

• from brownie import <contract_name>, accounts

In this following example, we want to test that favNum initializes to 0.

• deploy the contract

• retrieve the starting value

• compare it with expected starting value

from brownie import SimpleStorage, accounts

def test_deploy():
    # Arrange - setup
    account = accounts[0]

    # Act
    simple_storage = SimpleStorage.deploy({"from": account})
    starting_value = simple_storage.retrieve()
    expected_value = 0

    # Assert
    assert expected_value == starting_value

To run this test, input: brownie test in terminal:

If we get a green dot at the end like above, all tests were successful.

Test updating storage variable

from brownie import SimpleStorage, accounts

def test_deploy():
    # Arrange - setup
    account = accounts[0]

    # Act
    simple_storage = SimpleStorage.deploy({"from": account})
    starting_value = simple_storage.retrieve()
    expected_value = 0

    # Assert
    assert expected_value == starting_value

def test_update_storage():
    # Arrange - setup
    account = accounts[0]
    simple_storage = SimpleStorage.deploy({"from": account})

    # Act
    expected = 15
    simple_storage.store(expected,{"from": account}) #store 15

    # Assert
    assert expected == simple_storage.retrieve()

• deploy contract

• update favNum storage variable to be 15

• retrieve storage variable and compare with expected.

Tips

To test 1 function

brownie test -k <function name> brownie test -k test_update_storage

To get into interactive mode:

brownie test --pdb

when a test fails, or an error is encountered, terminal will convert to an interactive python shell:

we can observe the values of variables by typing them in and their values will be returned.

reference the other brownie flags from pytest documentation

get accounts

from brownie import SimpleStorage, accounts, network

#if on non-persistent dev netowrk, use generated ganache account
#else look in.yaml file for our MM account's PK
def get_accounts():
    if network.show_active() == "development":
        return accounts[0]                  #use ganache generated account.
    else:
        return accounts.add(config["wallets"]["wallet1"])  #look in config.yaml
        
def test_deploy():
    # Arrange - setup
    account = get_accounts()

#etc

Negative tests

Lets say you want to do a test that results in a revert. Like testing a function that only the owner can call, but calling it from a non-owner address.

We will use pytest to skip tests that we only want conducted in our private local chains (pip install pytest)

test_fund_me.py

def test_OwnerWithdraw():
    if network.show_active() not in LOCAL_BLOCKCHAIN_ENV:
       pytest.skip("ONLY FOR LOCAL TESTING!")

    if len(FundMe) <= 0: 
        fund_me = deploy_fund_me()
    fund_me = FundMe[-1]

    bad_actor = accounts.add()
    fund_me.withdraw({"from": bad_actor})

You would expect a revert to be thrown, like below, reflecting that an exception had occurred:

exception thrown

How can we conduct a negative test properly?

the correct form of the test would be:

from brownie import exceptions

def test_only_owner_can_withdraw():
    if network.show_active() not in LOCAL_BLOCKCHAIN_ENVIRONMENTS:
        pytest.skip("only for local testing")
    fund_me = deploy_fund_me()
    bad_actor = accounts.add()
    with pytest.raises(exceptions.VirtualMachineError):
        fund_me.withdraw({"from": bad_actor})

Where should i run my tests

1. Brownie Ganache chain with Mocks: Always

   1. (tests should clear on brownie spun up ganache-cli env)

2. Testnet: Always (but only for integration testing)

3. Brownie mainnet-fork: Optional

4. Custom mainnet-fork: Optional

5. Self/Local Ganache: Not necessary, but good for tinkering