Add tests for CaffeineCacheMetrics

See micrometer-metrics/micrometer#1254

build.gradle

@@ -29,11 +29,15 @@ repositories {
 }
 
 //ext['micrometer.version'] = '1.0.10-SNAPSHOT'
+ext['micrometer.version'] = '1.2.0-SNAPSHOT'
+ext['caffeine.version'] = '2.7.0'
 
 dependencies {
     compile("org.springframework.boot:spring-boot-starter-web")
     compile("org.springframework.boot:spring-boot-starter-actuator")
 
+    compile("com.github.ben-manes.caffeine:caffeine")
+
     testCompile("org.springframework.boot:spring-boot-starter-test")
 }
 

src/test/java/io/micrometer/core/instrument/binder/cache/CaffeineCacheMetricsTests.java

@@ -0,0 +1,38 @@
+package io.micrometer.core.instrument.binder.cache;
+
+import com.github.benmanes.caffeine.cache.AsyncCache;
+import com.github.benmanes.caffeine.cache.AsyncLoadingCache;
+import com.github.benmanes.caffeine.cache.Cache;
+import com.github.benmanes.caffeine.cache.LoadingCache;
+import com.github.benmanes.caffeine.cache.stats.CacheStats;
+import io.micrometer.core.instrument.simple.SimpleMeterRegistry;
+import org.junit.Test;
+
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+public class CaffeineCacheMetricsTests {
+
+	@Test
+	public void monitorWithAsyncLoadingCache() {
+		LoadingCache loadingCache = mock(LoadingCache.class);
+		CacheStats stats = new CacheStats(0L, 0L, 0L, 0L, 0L, 0L, 0L);
+		when(loadingCache.stats()).thenReturn(stats);
+
+		AsyncLoadingCache asyncLoadingCache = mock(AsyncLoadingCache.class);
+		when(asyncLoadingCache.synchronous()).thenReturn(loadingCache);
+		CaffeineCacheMetrics.monitor(new SimpleMeterRegistry(), asyncLoadingCache, "test");
+	}
+
+	@Test
+	public void monitorWithAsyncCache() {
+		Cache cache = mock(Cache.class);
+		CacheStats stats = new CacheStats(0L, 0L, 0L, 0L, 0L, 0L, 0L);
+		when(cache.stats()).thenReturn(stats);
+
+		AsyncCache asyncCache = mock(AsyncCache.class);
+		when(asyncCache.synchronous()).thenReturn(cache);
+		CaffeineCacheMetrics.monitor(new SimpleMeterRegistry(),asyncCache, "test");
+	}
+
+}