What tests did you have to write? What coverage did you maintain?

In my practice, I have written various types of tests:

• Unit tests — to verify individual functions and methods to ensure they work correctly in isolation.
• Integration tests — to check the interaction between system components, such as between a service and a database.
• Functional tests — to verify business logic and user scenarios.
• Performance tests — to assess speed and load.

Regarding coverage, I usually aim to keep unit test coverage at no less than 70-80% to ensure sufficient confidence in code stability. At the same time, the quality of tests and checking key scenarios are more important than just a high coverage percentage.

An example of usage in Java with JUnit:

@Test
public void testCalculateBalance() {
    Account account = new Account();
    account.deposit(100);
    account.withdraw(30);
    assertEquals(70, account.getBalance());
}

I also used coverage analysis tools, such as JaCoCo, to monitor and improve test quality.