As of 0.20.6 I get a NoClassDefFoundError when starting ElasticSearch within test classes. Looks like you just need to express the xerial snappy dependency in your pom file.

Here's the error:

18:28:59.930 [main] INFO org.elasticsearch.plugins - [Jones, Hugh] loaded [], sites []
18:28:59.941 [main] DEBUG o.elasticsearch.common.compress.lzf - using [UnsafeChunkDecoder] decoder
18:28:59.949 [main] DEBUG org.elasticsearch.common.compress - failed to load xerial snappy-java
java.lang.NoClassDefFoundError: org/xerial/snappy/Snappy
at org.elasticsearch.common.compress.snappy.xerial.XerialSnappy.(XerialSnappy.java:42) ~[elasticsearch-0.20.6.jar:na]
at org.elasticsearch.common.compress.CompressorFactory.(CompressorFactory.java:58) ~[elasticsearch-0.20.6.jar:na]
at org.elasticsearch.node.internal.InternalNode.(InternalNode.java:134) [elasticsearch-0.20.6.jar:na]
at org.elasticsearch.node.NodeBuilder.build(NodeBuilder.java:159) [elasticsearch-0.20.6.jar:na]
at org.elasticsearch.node.NodeBuilder.node(NodeBuilder.java:166) [elasticsearch-0.20.6.jar:na]