Test

This is a pre-configured set of rules meant to be used in autotests.

Is based on the Main rule set.

Full configuration: analysis_options_test.yaml

Below are details on some of the rules; rationale for their usage or configuration.

avoid_late_keyword

State: Disabled.

Late keyword is allowed in tests in order to enable the use of custom mocks and fakes.

It has several benefits over its alternatives (see below):

• Allows initialising the mocks inside the setUp method.
• Allows resetting mocks by re-initialising them inside setUp
• Allows passing the mock inside functions that require non-null params, without any extra force-unwraps or null checks.
• Uninitialized test mocks are clearly traceable.
• Produces minimal visual clutter.

Alternatives considered:

1. Making the mocks final and non-nullable, and adding a reset() method to them, which would return the mock/fake to its initial state.
   • Works well with generated code from testing libraries like mockito.
   • It's less practical with hand-written mocks, where it's possible to add a piece of state and forget to reset it, which might lead to hard-to-trace errors. Usually re-instantiating a test mock simplifies its code and prevents such errors altogether, but that requires making the field non-final, as well as delegating its initialisation to the setUp method.
2. Making the mocks nullable, and using .? access syntax.
   • In many cases will cause harder-to-trace testcase failures, if a mock was not initialised.
   • Does not allow passing the nullable mock into constructors/methods that require a non-nullable input.
3. Making the mocks nullable, and adding null-checks in test code.
   • Will lead to significant code bloat, without much benefit, as a null mock will still usually lead to a failed test.
4. Making the mocks nullable and using the "bang" operator (!):
   • In terms of behavior similar to late, but requires using the operator in many places inside the test code, adding uninformative visual noise.
   • The use of this operator is also discouraged by the main ruleset.

function_lines_of_code

State: Disabled

Tests usually organized in one large main() function making this rule not applicable.

Given the quite large threshold configured for this metric we considered extracting test body into separate function, but that means that we'll have to do one of the following:

• Pass Test Context that contains all defined variables from main to every function call.
• Moving the variables to the Global State.

Both options didn't look right, so we decided that tests are ok to be long.

prefer_match_file_name

State: Disabled.

It's acceptable to include stubs or other helper classes into the test file.