public void TestPutMetaData()
{
string expectedKey = "testKey";
string expectedValue = "testValue";
_metricsLogger.PutMetadata(expectedKey, expectedValue);
_metricsLogger.Flush();
var rootNode = typeof(MetricsContext)
.GetField("_rootNode", System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance)
.GetValue(_sink.MetricsContext) as RootNode;
rootNode.AWS.CustomMetadata.TryGetValue(expectedKey, out var actualValue);
Assert.Equal(expectedValue, actualValue);
}