Java Stack栈的单元测试方法

在Java中，我们可以使用JUnit框架来进行单元测试

首先，确保已经在项目中添加了JUnit依赖。如果使用Maven，可以在pom.xml文件中添加以下依赖：

<dependencies>
    <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <version>4.13.2</version>
        <scope>test</scope>
    </dependency>
</dependencies>

接下来，创建一个名为MyStack.java的Java Stack类：

public class MyStack<T> {
    private Node<T> top;
    private int size;

    private static class Node<T> {
        T data;
        Node<T> next;

        public Node(T data) {
            this.data = data;
        }
    }

    public void push(T value) {
        Node<T> newNode = new Node<>(value);
        newNode.next = top;
        top = newNode;
        size++;
    }

    public T pop() {
        if (isEmpty()) {
            throw new IllegalStateException("Stack is empty");
        }
        T value = top.data;
        top = top.next;
        size--;
        return value;
    }

    public T peek() {
        if (isEmpty()) {
            throw new IllegalStateException("Stack is empty");
        }
        return top.data;
    }

    public boolean isEmpty() {
        return top == null;
    }

    public int size() {
        return size;
    }
}

现在，我们可以编写一个名为MyStackTest.java的单元测试类：

import org.junit.Before;
import org.junit.Test;
import static org.junit.Assert.*;

public class MyStackTest {
    private MyStack<Integer> stack;

    @Before
    public void setUp() {
        stack = new MyStack<>();
    }

    @Test
    public void testPushAndPop() {
        stack.push(1);
        stack.push(2);
        stack.push(3);

        assertEquals(3, stack.pop());
        assertEquals(2, stack.pop());
        assertEquals(1, stack.pop());
    }

    @Test
    public void testPeek() {
        stack.push(1);
        stack.push(2);
        stack.push(3);

        assertEquals(3, stack.peek());
    }

    @Test(expected = IllegalStateException.class)
    public void testPopOnEmptyStack() {
        stack.pop();
    }

    @Test(expected = IllegalStateException.class)
    public void testPeekOnEmptyStack() {
        stack.peek();
    }

    @Test
    public void testIsEmpty() {
        assertTrue(stack.isEmpty());

        stack.push(1);
        assertFalse(stack.isEmpty());

        stack.pop();
        assertTrue(stack.isEmpty());
    }

    @Test
    public void testSize() {
        assertEquals(0, stack.size());

        stack.push(1);
        assertEquals(1, stack.size());

        stack.push(2);
        assertEquals(2, stack.size());

        stack.pop();
        assertEquals(1, stack.size());
    }
}

这个测试类包含了针对MyStack类的各种方法的测试用例，包括push、pop、peek、isEmpty和size。通过运行这些测试用例，我们可以确保MyStack类的实现是正确的。