What is the purpose of the expect actual construction in the testing process?

The expect actual construction is used in testing to verify that the actual result (actual) matches the expected value (expect). This allows for automating the validation of code correctness.

For example, in Kotlin using the Kotest library:

val actual = sum(2, 3)
expect(actual).toBe(5)

Here, expect(actual) creates a wrapper object around the actual value, to which verification methods (toBe(5)) are applied, comparing it with the expected result. If the values do not match, the test is considered failed.

Thus, expect actual is the basis for assertions in tests, providing automatic validation of code behavior.