http://www.gradle.org/docs/current/dsl/org.gradle.api.tasks.testing.Test.html#org.gradle.api.tasks.testing.Test:beforeTest%28groovy.lang.Closure%29
http://www.gradle.org/docs/current/dsl/org.gradle.api.tasks.testing.Test.html#org.gradle.api.tasks.testing.Test:afterTest%28groovy.lang.Closure%29

Multiple unit tests create schemas, but then do not clean them up. This eventually causes collisions, especially if the table had constraints added. Have beforeTest/afterTest scripted in Gradle to force cleanup.