Writing good tests for object-oriented code requires some skills and practices. To help you write effective and readable tests, consider using a testing framework that supports object-oriented features, such as JUnit for Java, RSpec for Ruby, or PyTest for Python. Additionally, follow the AAA pattern: arrange the test data and objects, act on the objects and methods under test, and assert the expected results and behaviors. You should also use descriptive and meaningful names for your test methods and classes that follow the convention of your testing framework and language. Moreover, use the given-when-then format to structure your test cases and scenarios, describing the preconditions, actions, and outcomes of your tests. To isolate and simulate the dependencies and interactions of your objects, use mocks, stubs, and fakes to avoid external factors that may affect your tests. Additionally, use test doubles such as inheritance, composition, or delegation to override or extend the behavior of your objects for testing purposes. Finally, use test-driven design patterns like dependency injection, factory method or template method to make your code more testable and modular.