GContracts provides annotations to implement interface contracts aka design by contract in Groovy classes.
'org.gcontracts:gcontracts:1.0.2'
<dependency>
<groupId>org.gcontracts</groupId>
<artifactId>gcontracts</artifactId>
<version>1.0.2</version>
</dependency>
<dependency org="org.gcontracts" name="gcontracts" rev="1.0.2"/>
"org.gcontracts", "gcontracts", "1.0.2"