container-core/src/test/java/com/yahoo/container/jdisc/state/MetricSnapshotTest.java


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// Copyright 2016 Yahoo Inc. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.container.jdisc.state;

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

public class MetricSnapshotTest {
    /**
     * Aggregate metrics are not cloned into new snapshot. In turn, a metric
     * set with only aggregates will be added as an empty set if we do not
     * filter these away at clone time. This test ensures that we do just that.
     * If/when we start carrying aggregates across snapshots, this test will
     * most likely be deprecated.
     */
    @Test
    public void emptyMetricSetNotAddedToClonedSnapshot() {
        final StateMetricContext ctx = StateMetricContext.newInstance(null);
        MetricSnapshot snapshot = new MetricSnapshot();
        snapshot.add(ctx, "foo", 1234);
        MetricSnapshot newSnapshot = snapshot.createSnapshot();
        assertFalse(newSnapshot.iterator().hasNext());
    }
}