What components and scenarios do you prefer to cover with automated tests when developing a new microservice?

When developing a new microservice, I aim to cover the following components and scenarios with automated tests:

• Unit tests for business logic: testing individual methods and classes without external dependencies.
• Integration tests for interaction with databases, external APIs, and other services.
• Controller (API) tests to ensure endpoints handle requests correctly and return expected responses.
• Validation checks for input data and error handling.

Main scenarios:

• Positive cases where all data is correct.
• Negative cases, such as incorrect input data or errors when interacting with external services.
• Boundary conditions and exceptions.

Example of a unit test in Java using JUnit 5:

@Test
void testCalculateDiscount() {
    OrderService service = new OrderService();
    double discount = service.calculateDiscount(1000);
    assertEquals(100, discount);
}