2.11、嵌套测试
@Nested
测试让测试编写人员能够更多得表述出几个测试组之前得关系。下面是一个详细得例子。
import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertFalse;
import static org.junit.jupiter.api.Assertions.assertThrows;
import static org.junit.jupiter.api.Assertions.assertTrue;
import java.util.EmptyStackException;
import java.util.Stack;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.DisplayName;
import org.junit.jupiter.api.Nested;
import org.junit.jupiter.api.Test;
@DisplayName("A stack")
class TestingAStackDemo {
Stack<Object> stack;
@Test
@DisplayName("is instantiated with new Stack()")
void isInstantiatedWithNew() {
new Stack<>();
}
@Nested
@DisplayName("when new")
class WhenNew {
@BeforeEach
void createNewStack() {
stack = new Stack<>();
}
@Test
@DisplayName("is empty")
void isEmpty() {
assertTrue(stack.isEmpty());
}
@Test
@DisplayName("throws EmptyStackException when popped")
void throwsExceptionWhenPopped() {
assertThrows(EmptyStackException.class, stack::pop);
}
@Test
@DisplayName("throws EmptyStackException when peeked")
void throwsExceptionWhenPeeked() {
assertThrows(EmptyStackException.class, stack::peek);
}
@Nested
@DisplayName("after pushing an element")
class AfterPushing {
String anElement = "an element";
@BeforeEach
void pushAnElement() {
stack.push(anElement);
}
@Test
@DisplayName("it is no longer empty")
void isNotEmpty() {
assertFalse(stack.isEmpty());
}
@Test
@DisplayName("returns the element when popped and is empty")
void returnElementWhenPopped() {
assertEquals(anElement, stack.pop());
assertTrue(stack.isEmpty());
}
@Test
@DisplayName("returns the element when peeked but remains not empty")
void returnElementWhenPeeked() {
assertEquals(anElement, stack.peek());
assertFalse(stack.isEmpty());
}
}
}
}
内部类中只有非静态内部类才可以作为
@Nested
测试类。嵌套可以是任意深度的,这些内部类被认为是测试类家族的完整成员,只有一个例外:@BeforeAll
和@AfterAll
默认情况下不生效。原因是Java
在非静态内部类中不允许有静态成员。但是这个限制可以通过使用@Nested
和@TestInstance(Lifecycle.PER_CLASS)
来避免。