The previously used approach of
project(':smack-core').sourceSets.test.runtimeClasspath
caused the 'eclipse' target to produce duplicate classpath entries in
.classpath when run with Gradle >= 2.6. It also relied on Gradle
internals.
Instead we now use
project(path: ":smack-core", configuration: "testRuntime")
project(path: ":smack-core", configuration: "archives")
to be able to use test classes from other subprojects (usually
smack-core) in e.g. smack-extensions. The 'archives' configuration
includes the test jar.
See also https://discuss.gradle.org/t/11784
Thanks to Lari Hotari for helping with this issue.
