Spring Boot Guava CacheMetrics Tests

import com.google.common.cache.Cache;
import com.google.common.cache.CacheStats;
import org.junit.Before;
import org.junit.Test;
import org.springframework.boot.actuate.metrics.Metric;
import org.springframework.cache.concurrent.ConcurrentMapCache;
import org.springframework.cache.guava.GuavaCache;
import org.springframework.cache.support.SimpleCacheManager;

import static java.util.Arrays.asList;
import static org.hamcrest.Matchers.contains;
import static org.hamcrest.Matchers.is;
import static org.junit.Assert.assertThat;
import static org.mockito.Mockito.mock;
import static org.mockito.Mockito.when;

public class CacheMetricsTests {

    private SimpleCacheManager cacheManager;

    private CacheMetrics cacheMetrics;

    @Before
    public void setUp() {
        this.cacheManager = new SimpleCacheManager();
        this.cacheMetrics = new CacheMetrics(cacheManager);
    }

    @Test
    public void cache_metrics_should_return_metrics() {
        Cache cache1 = mock(Cache.class);
        CacheStats cache1Stats = new CacheStats(40L, 20L, 0L, 0L, 0L, 10L);
        when(cache1.size()).thenReturn(5L);
        when(cache1.stats()).thenReturn(cache1Stats);

        Cache cache2 = mock(Cache.class);
        CacheStats cache2Stats = new CacheStats(20L, 40L, 0L, 0L, 0L, 5L);
        when(cache2.size()).thenReturn(2L);
        when(cache2.stats()).thenReturn(cache2Stats);

        cacheManager.setCaches(asList(
                new GuavaCache("cache1", cache1),
                new GuavaCache("cache2", cache2)
        ));
        cacheManager.afterPropertiesSet();

        Metric<?>[] metrics = cacheMetrics.metrics().toArray(new Metric<?>[] {});

        assertThat(metrics.length, is(14));

        assertThat(metrics[0].getName(), is("cache.cache1.size"));
        assertThat(metrics[0].getValue(), is(5L));
        assertThat(metrics[1].getName(), is("cache.cache1.eviction_count"));
        assertThat(metrics[1].getValue(), is(10L));
        assertThat(metrics[2].getName(), is("cache.cache1.hit_count"));
        assertThat(metrics[2].getValue(), is(40L));
        assertThat(metrics[3].getName(), is("cache.cache1.hit_rate"));
        assertThat(metrics[3].getValue(), is(0.6666666666666666)); // hit_count / request_count
        assertThat(metrics[4].getName(), is("cache.cache1.miss_count"));
        assertThat(metrics[4].getValue(), is(20L));
        assertThat(metrics[5].getName(), is("cache.cache1.miss_rate"));
        assertThat(metrics[5].getValue(), is(0.3333333333333333)); // miss_count / request_count
        assertThat(metrics[6].getName(), is("cache.cache1.request_count"));
        assertThat(metrics[6].getValue(), is(60L)); // hit_count + miss_count

        assertThat(metrics[7].getName(), is("cache.cache2.size"));
        assertThat(metrics[7].getValue(), is(2L));
        assertThat(metrics[8].getName(), is("cache.cache2.eviction_count"));
        assertThat(metrics[8].getValue(), is(5L));
        assertThat(metrics[9].getName(), is("cache.cache2.hit_count"));
        assertThat(metrics[9].getValue(), is(20L));
        assertThat(metrics[10].getName(), is("cache.cache2.hit_rate"));
        assertThat(metrics[10].getValue(), is(0.3333333333333333)); // hit_count / request_count
        assertThat(metrics[11].getName(), is("cache.cache2.miss_count"));
        assertThat(metrics[11].getValue(), is(40L));
        assertThat(metrics[12].getName(), is("cache.cache2.miss_rate"));
        assertThat(metrics[12].getValue(), is(0.6666666666666666)); // miss_count / request_count
        assertThat(metrics[13].getName(), is("cache.cache2.request_count"));
        assertThat(metrics[13].getValue(), is(60L)); // hit_count + miss_count
    }

    @Test
    public void cahe_metrics_should_return_no_metrics_when_cache_is_no_guava_cache() {
        cacheManager.setCaches(asList(new ConcurrentMapCache("cache1")));
        cacheManager.afterPropertiesSet();

        assertThat(cacheManager.getCacheNames(), contains("cache1")); // make sure there is a cache instance
        assertThat(cacheMetrics.metrics().size(), is(0)); // metrics should be empty
    }
}