I need help with os.environ values when working with pytest. I have a few environ variables in init.py file, where they get picked up if pytest is executed. How would I mock them?

When working with pytest and needing to mock environment variables that are accessed via

os.environ

, you can use the

monkeypatch

fixture provided by pytest. This fixture allows you to temporarily modify or add environment variables during your test functions, and it will ensure that the changes do not affect other tests or the system environment after the test finishes. Here's a step-by-step guide on how to use

monkeypatch

to mock environment variables: 1. Import the

monkeypatch

fixture in your test function by including it as an argument to the function. 2. Use the

monkeypatch.setenv

method to set the environment variable to the value you want for the test. 3. Write your test code that uses the environment variable. 4. Run your tests. The

monkeypatch

fixture will ensure that the environment variable is set for the duration of the test and then revert to its original state afterward. Here's an example of how you might use

monkeypatch

in a pytest test function:

python def test_my_function(monkeypatch):     # Mock the environment variable     monkeypatch.setenv('MY_ENV_VAR', 'mock_value')      # Now, when your code accesses 'MY_ENV_VAR' via os.environ,     # it will see 'mock_value' instead of the actual value.     result = my_function_that_uses_env_var()      # Perform your test assertions     assert result == 'expected_result_based_on_mock_value'

In this example,

my_function_that_uses_env_var

would be the function you're testing that accesses the

MY_ENV_VAR

environment variable. The

monkeypatch.setenv

call ensures that within this test,

MY_ENV_VAR

will have the value

'mock_value'

. Remember that the mocking only applies to the test in which you call

monkeypatch.setenv

, and it will not affect other tests or the actual environment variables on your system.

@Scout this is my case. And my pytest fails at os.environ["GOOGLE_APPLICATION_CREDENTIALS"]. HOw to avoid this?

If your pytest is failing because it expects the

GOOGLE_APPLICATION_CREDENTIALS

environment variable to be set, you can use the

monkeypatch

fixture in pytest to mock this environment variable during your tests. Here's how you can do it: 1. Add the

monkeypatch

fixture to your test function's arguments. 2. Use

monkeypatch.setenv

to set the

GOOGLE_APPLICATION_CREDENTIALS

environment variable to a mock value that points to a valid credentials file for the duration of the test. 3. Ensure that you have a mock credentials file at the specified path, or your code is able to handle the mock path accordingly. Here's an example of how to mock the

GOOGLE_APPLICATION_CREDENTIALS

in a pytest test:

python def test_my_google_function(monkeypatch, tmp_path):     # Create a temporary mock credentials file     mock_credentials = tmp_path / "mock_credentials.json"     mock_credentials.write_text('{"type": "service_account", "project_id": "my-mock-project"}')      # Set the GOOGLE_APPLICATION_CREDENTIALS environment variable to point to the mock file     monkeypatch.setenv("GOOGLE_APPLICATION_CREDENTIALS", str(mock_credentials))      # Now, when your code accesses 'GOOGLE_APPLICATION_CREDENTIALS' via os.environ,     # it will see the path to the mock credentials file.     result = my_google_function()      # Perform your test assertions     assert result == 'expected_result'

In this example,

tmp_path

is a pytest fixture that provides a temporary directory unique to the test function. A mock credentials file is created in this directory, and the

GOOGLE_APPLICATION_CREDENTIALS

environment variable is set to point to this file. The

my_google_function

is the function you're testing that uses the

GOOGLE_APPLICATION_CREDENTIALS

environment variable. By using

monkeypatch.setenv

, the environment variable will only be set for the duration of the test, and it will not affect other tests or the actual environment on your system. Make sure that the mock credentials file you create is sufficient for your code to run without actually needing to authenticate with Google Cloud services.

@Scout this is my case. # Deployment type deployment_name = os.getenv("DAGSTER_DEPLOYMENT", "prod") # Google credentials os.environ["GOOGLE_APPLICATION_CREDENTIALS"] = os.getenv("GOOGLE_CREDS") defs = Definitions( assets=combined_assets, schedules=[bs_job_schedule], # asset_checks=qualitychecks_test, resources=resources[deployment_name], ). And my pytest fails at os.environ["GOOGLE_APPLICATION_CREDENTIALS"]. HOw to avoid this?

In the case you've described, it looks like your code is setting the

GOOGLE_APPLICATION_CREDENTIALS

environment variable directly within the module's code. This can cause issues during testing because the

os.getenv("GOOGLE_CREDS")

call may return

None

if the

GOOGLE_CREDS

environment variable is not set, leading to a failure when trying to set

os.environ["GOOGLE_APPLICATION_CREDENTIALS"]

. To avoid this issue during testing with pytest, you can use the

monkeypatch

fixture to mock the

GOOGLE_CREDS

environment variable before the code that sets

GOOGLE_APPLICATION_CREDENTIALS

is executed. Here's how you can modify your test to handle this:

python def test_my_dagster_deployment(monkeypatch, tmp_path):     # Create a temporary mock credentials file     mock_credentials = tmp_path / "mock_credentials.json"     mock_credentials.write_text('{"type": "service_account", "project_id": "my-mock-project"}')      # Mock the GOOGLE_CREDS environment variable to point to the mock file     monkeypatch.setenv("GOOGLE_CREDS", str(mock_credentials))      # Now, when your code accesses 'GOOGLE_CREDS' via os.getenv,     # it will receive the path to the mock credentials file.     # This will then set the GOOGLE_APPLICATION_CREDENTIALS environment variable correctly.     from my_module import defs  # Import here to ensure the environment variable is set first      # Perform your test logic and assertions     # ...

In this example, you create a mock credentials file and use

monkeypatch.setenv

to set the

GOOGLE_CREDS

environment variable to the path of this mock file. When your code runs, it will pick up this mock path and set the

GOOGLE_APPLICATION_CREDENTIALS

environment variable accordingly. Please note that you should import the module containing the

defs

variable inside the test function after setting the mock environment variable. This ensures that the environment variable is mocked before the code that depends on it is executed. By using this approach, you avoid the issue of

os.getenv("GOOGLE_CREDS")

returning

None

, and your tests should no longer fail due to the

GOOGLE_APPLICATION_CREDENTIALS

environment variable not being set.

@Scout so lets say this is the test case that I would like to evaluate. How would a full example look like with monkeypatching? def test_generate_bs_assets_correct(): spec = {"table_name": "test_table", "destination": "test_dataset.test_table"} load_table_asset, save_data_bq_asset = generate_bs_assets(spec) assert ( load_table_asset.asset_and_check_keys_by_output_name["result"][0][0] == f"load_data_{spec['table_name']}" ) assert ( save_data_bq_asset.asset_and_check_keys_by_output_name["result"][0][0] == f"bs_save_data_bq_{spec['table_name']}" )

To fully mock the environment variables in your test case using

monkeypatch

, you would need to do the following: 1. Use the

monkeypatch

fixture to set the environment variables that are expected by your code. 2. Import the code that uses these environment variables within the test function after setting the mocks to ensure they are applied correctly. 3. Run your assertions as normal. Here's how you could write your test case with `monkeypatch`:

python
def test_generate_bs_assets_correct(monkeypatch, tmp_path):
    # Mock the environment variables that your code expects
    # For example, if your code requires 'DAGSTER_DEPLOYMENT' and 'GOOGLE_CREDS'
    monkeypatch.setenv("DAGSTER_DEPLOYMENT", "test")
    
    # Create a temporary mock credentials file for 'GOOGLE_CREDS'
    mock_credentials = tmp_path / "mock_credentials.json"
    mock_credentials.write_text('{"type": "service_account", "project_id": "my-mock-project"}')
    
    # Set the 'GOOGLE_CREDS' environment variable to point to the mock file
    monkeypatch.setenv("GOOGLE_CREDS", str(mock_credentials))

    # Import the module/function after setting the environment variables
    from my_module import generate_bs_assets

    # Call the function you want to test
    spec = {"table_name": "test_table", "destination": "test_dataset.test_table"}
    load_table_asset, save_data_bq_asset = generate_bs_assets(spec)

    # Perform your test assertions
    assert (
        load_table_asset.asset_and_check_keys_by_output_name["result"][0][0]
        == f"load_data_{spec['table_name']}"
    )
    assert (
        save_data_bq_asset.asset_and_check_keys_by_output_name["result"][0][0]
        == f"bs_save_data_bq_{spec['table_name']}"
    )

In this example,

monkeypatch.setenv

is used to set both

DAGSTER_DEPLOYMENT

and

GOOGLE_CREDS

environment variables before the

generate_bs_assets

function is imported and executed. This ensures that when the code within

generate_bs_assets

runs, it uses the mocked environment variables. Remember to replace

"my_module"

with the actual name of the module where

generate_bs_assets

is defined. Also, ensure that the

tmp_path

fixture is used to create a temporary directory for the mock credentials file, which avoids any side effects on the actual file system. By following this pattern, you can isolate your tests from external dependencies such as environment variables and ensure that they are repeatable and reliable. Asset Checks on DBT Assets button Error on Asset Dependency with Multiple ... button Asset checks: severity and blocking mate... button Asset checks | Dagster button Thank you for your feedback!