SimpleAgedCache：为什么我无法让我的 SimpleAgedCache 通过测试？

Question

我是编码和编程新手，我在 GitHub 上发现了一个有趣的使用 JavaScript 的 SimpleAgedCache 练习。我觉得我已经完成了正确的编码，并且练习应该通过测试。然而，测试一直失败。有人可以向我解释为什么会出现这种情况以及我做错了什么吗？谢谢。

package test.collective;

import io.collective.SimpleAgedCache;
import org.junit.Before;
import org.junit.Test;

import java.time.Clock;
import java.time.Duration;
import java.time.Instant;
import java.time.ZoneId;

import static junit.framework.TestCase.*;

class ExpirableEntry {
    String key;
    String value;
    long expirationTime;

    ExpirableEntry(String key, String value, long expirationTime) {
        this.key = key;
        this.value = value;
        this.expirationTime = expirationTime;
    }
}

public class SimpleAgedCacheTest {
    private SimpleAgedCache empty;
    private SimpleAgedCache nonempty;

    private ExpirableEntry[] cacheArray;
    private Clock clock;
    private int size;

   public SimpleAgedCacheTest() {
       this.empty = new SimpleAgedCache();
       this.nonempty = new SimpleAgedCache();
       this.cacheArray = new ExpirableEntry[10];
       this.clock = Clock.systemUTC();
       this.size = 0;
   }

    public void put(String key, String value, long durationMillis) {
        long expirationTime = clock.instant().plusMillis(durationMillis).toEpochMilli();
        ExpirableEntry entry = new ExpirableEntry(key, value, expirationTime);
        cacheArray[size++] = entry;
    }

   public String get(String key) {
       for (int i = 0; i < size; i++) {
           ExpirableEntry entry = cacheArray[i];
           if (entry.key.equals(key) && !isExpired(entry)) {
               return entry.value;
           }
       }
       return null;
   }

    public boolean isEmpty() {
        return size == 0;
    }

    public int size() {
        return size;
    }
    private boolean isExpired(ExpirableEntry entry) {
        return clock.instant().toEpochMilli() > entry.expirationTime;
    }

    @Before
    public void setup() {

    nonempty.put("aKey", "aValue", 2000);
    nonempty.put("anotherKey", "anotherValue", 4000);
    }

    @Test
    public void isEmptyTest() {
        assertTrue(empty.isEmpty());
        assertFalse(nonempty.isEmpty());
    }

    @Test
    public void sizeTest() {
        assertEquals(0, empty.size());
        assertEquals(2, nonempty.size());
    }

    @Test
    public void getTest() {
        assertNull(empty.get("aKey"));
        assertEquals("anotherValue", nonempty.get("anotherKey"));
        assertEquals("aValue", nonempty.get("aKey"));

    }

    @Test
    public void getExpiredTest() {
        TestClock clock = new TestClock();

        SimpleAgedCache expired = new SimpleAgedCache(clock);
        expired.put("aKey", "aValue", 2000);
        expired.put("anotherKey", "anotherValue", 4000);

        clock.offset(Duration.ofMillis(3000));

        assertEquals("anotherValue", expired.get("anotherKey"));
        assertEquals(1, expired.size());
    }

    static class TestClock extends Clock {
        Duration offset = Duration.ZERO;

        @Override
        public ZoneId getZone() {
            return Clock.systemDefaultZone().getZone();
        }

        @Override
        public Clock withZone(ZoneId zone) {
            return Clock.offset(Clock.system(zone), offset);
        }

        @Override
        public Instant instant() {
            return Clock.offset(Clock.systemDefaultZone(), offset).instant();
        }

        public void offset(Duration offset) {
            this.offset = offset;
        }
    }
}

我尝试过翻转

的顺序

assertEquals("anotherValue", expired.get("anotherKey));

和

assertEquals(1, expired.size());

但没有效果。

   @Test
    public void getExpiredTest() {
        TestClock clock = new TestClock();

        SimpleAgedCache expired = new SimpleAgedCache(clock);
        expired.put("aKey", "aValue", 2000);
        expired.put("anotherKey", "anotherValue", 4000);

        clock.offset(Duration.ofMillis(3000));

        assertEquals("anotherValue", expired.get("anotherKey"));
        assertEquals(1, expired.size());

Answer 1

您永远不会递减

size

，无论缓存数组保存的过期项目数量如何，该值始终会增加：

 cacheArray[size++] = entry;

要解决此问题，您需要使

size()

计算具有条件

!isExpired(entry)

的条目数。