Testing an ape project is important and easy.

Test Structure

Tests must be located in a project’s tests/ directory. Each test file must start with test_ and have the .py extension, such as test_my_contract.py. Each test method within the file must also start with test_. The following is an example test:

def test_add():
    assert 1 + 1 == 2

NOTE: pytest assumes the actual value is on the left and the expected value is on the right.

Test Pattern

Tests are generally divisible into three parts:

  1. Set-up

  2. Invocation

  3. Assertion

In the example above, we created a fixture that deploys our smart-contract. This is an example of a ‘setup’ phase. Next, we need to call a method on our contract. Let’s assume there is an authorized_method() that requires the owner of the contract to make the transaction. If the sender of the transaction is not the owner, the transaction will fail to complete and will revert.

This is an example of how that test may look:

def test_authorization(my_contract, owner, not_owner):
    assert owner == my_contract.owner()

    with ape.reverts("!authorized"):


Ape has built-in test and fixture isolation for all pytest scopes. To disable isolation add the --disable-isolation flag when running ape test


Fixtures are any type of reusable instances of something with configurable scopes. pytest handles passing fixtures into each test method as test-time. To learn more about fixtures

Define fixtures for static data used by tests. This data can be accessed by all tests in the suite unless specified otherwise. This could be data as well as helpers of modules which will be passed to all tests.

A common place to define fixtures are in the conftest.py which should be saved under the test directory:

conftest.py is used to import external plugins or modules. By defining the following global variable, pytest will load the module and make it available for its test.

You can define your own fixtures or use existing ones. The ape-test plugin comes with fixtures you will likely want to use:

accounts fixture

You have access to test accounts. These accounts are automatically funded, and you can use them to transact in your tests. Access each test account by index from the accounts fixture:

def test_my_method(accounts):
    owner = accounts[0]
    receiver = accounts[1]

For code readability and sustainability, create your own fixtures using the accounts fixture:

import pytest

def owner(accounts):
    return accounts[0]

def receiver(accounts):
    return accounts[1]

def test_my_method(owner, receiver):

You can configure your accounts by changing the mnemonic or number_of_accounts settings in the test section of your ape-config.yaml file:

  mnemonic: test test test test test test test test test test test junk
  number_of_accounts: 5

If you are using a fork-provider, such as Hardhat, you can use impersonated accounts by accessing random addresses off the fixture:

def vitalik(accounts):
    return accounts["0xab5801a7d398351b8be11c439e05c5b3259aec9b"]

Using a fork-provider such as Hardhat, when using a contract instance as the sender in a transaction, it will be automatically impersonated:

def test_my_method(project, accounts):
    contract = project.MyContract.deploy(sender=accounts[0])
    other_contract = project.OtherContract.deploy(sender=accounts[0])

It has the same interface as the TestAccountManager, (same as doing accounts.test_accounts in a script or the console).

chain fixture

Use the chain fixture to access the connected provider or adjust blockchain settings.

For example, increase the pending timestamp:

def test_in_future(chain):
    chain.pending_timestamp += 86000
    assert "Something"
    chain.pending_timestamp += 86000
    assert "Something else"

It has the same interface as the ChainManager.

networks fixture

Use the networks fixture to change the active provider in tests.

def test_multi_chain(networks):
    assert "Something"  # Make assertion in root network
    # NOTE: Assume have ecosystem named "foo" with network "local" and provider "bar"
    with networks.foo.local.use_provider("bar"):
        assert "Something else"

It has the same interface as the NetworkManager.

project fixture

You also have access to the project you are testing. You will need this to deploy your contracts in your tests.

import pytest

def owner(accounts):
    return accounts[0]

def my_contract(project, owner):
    #           ^ use the 'project' fixture from the 'ape-test' plugin
    return owner.deploy(project.MyContract)

It has the same interface as the ProjectManager.

Ape testing commands

ape test

To run a particular test:

ape test test_my_contract

Use ape test -I to open the interactive mode at the point of exception. This allows the user to inspect the point of failure in your tests.

ape test test_my_contract -I -s

Test Providers

Out-of-the-box, your tests run using the eth-tester provider, which comes bundled with ape. If you have geth installed, you can use the ape-geth plugin that also comes with ape.

ape test --network ethereum:local:geth

Each testing plugin should work the same way. You will have access to the same test accounts.

Another option for testing providers is the ape-hardhat plugin, which does not come with ape but can be installed by including it in the plugins list in your ape-config.yaml file or manually installing it using the command:

ape plugins install hardhat

Advanced Testing Tips

If you want to use sample projects, follow this link to Ape Academy.

project                     # The root project directory
└── tests/                  # Project tests folder, ran using the 'ape test' command to run all tests within the folder.
    └── conftest.py         # A file to define global variable for testing 
    └── test_accounts.py    # A test file, if you want to ONLY run one test file you can use 'ape test test_accounts.py' command
    └── test_mint.py        # A test file

Here is an example of a test function from a sample NFT project

def test_account_balance(project, owner, receiver, nft):
    quantity = 1
    nft.mint(receiver, quantity, ["0"], value=nft.PRICE() * quantity, sender=owner)
    actual = project.balanceOf(receiver)
    expect = quantity
    assert actual == expect

Multi-chain Testing

The Ape framework supports connecting to alternative providers in tests. The easiest way to achieve this is to use the networks provider context-manager.

# Switch to Fantom mid test
def test_my_fantom_test(networks):
    # The test starts in 1 ecosystem but switches to another
    assert networks.provider.network.ecosystem.name == "ethereum"
    with networks.fantom.local.use_provider("test") as provider:
        assert provider.network.ecosystem.name == "fantom"
    # You can also use the context manager like this:
    with networks.parse_network_choice("fantom:local:test") as provider:
       assert provider.network.ecosystem.name == "fantom"

You can also set the network context in a context-manager pytest fixture:

import pytest

def stark_contract(networks, project):
    with networks.parse_network_choice("starknet:local"):
        yield project.MyStarknetContract.deploy()

def test_starknet_thing(stark_contract, stark_account):
    # Uses the starknet connection via the stark_contract fixture
    receipt = stark_contract.my_method(sender=stark_account)
    assert not receipt.failed

When you exit a provider’s context, Ape does not disconnect the provider. When you re-enter that provider’s context, Ape uses the previously-connected provider. At the end of the tests, Ape disconnects all the providers. Thus, you can enter and exit a provider’s context as much as you need in tests.