What techniques or approaches do you use when writing unit tests?

When writing unit tests, I use the following techniques and approaches:

• Isolation of the tested code: tests should verify only one unit of functionality, without dependence on external services or state.
• Use of mocks and stubs: to replace external dependencies, ensuring tests are fast and reliable.
• Clear naming of tests: names should reflect what exactly is being tested and under what conditions.
• Coverage of various scenarios: positive, negative, boundary cases.
• Automation of test execution: integration with CI/CD for timely detection of regressions.

Example in Swift using XCTest:

func testCalculateSum_WithPositiveNumbers_ReturnsCorrectSum() {
    let calculator = Calculator()
    let result = calculator.calculateSum(a: 2, b: 3)
    XCTAssertEqual(result, 5)
}

Here, the test checks that the calculateSum method correctly adds two positive numbers.