There shouldn't be any conflict between your and Gradle's Guava classes when running tests. Would you be able to provide a self-contained reproducible example?

Yes, actually the interaction is a bit more complex. We pull in guava and hive-exec is the shaded jar containing guava. It occurs with a simple module with the following

dependencies {
compile group: 'com.google.guava', name: 'guava', version: '15.+'
compile group: 'org.apache.hive', name: 'hive-exec', version: '0.12.0'
testCompile group: 'junit', name: 'junit', version: '4.11'
}

Does your (main or test) code make use of `org.gradle.internal.SystemProperties`?

The problem shows up even with a simple empty test when running gradle test in combination with this build file

apply plugin: 'java'

sourceCompatibility = 1.7
version = '1.0'

repositories {
mavenCentral()
}

dependencies {
compile group: 'com.google.guava', name: 'guava', version: '15.+'
compile group: 'org.apache.hive', name: 'hive-exec', version: '0.12.0'
testCompile group: 'junit', name: 'junit', version: '4.11'
}

import org.junit.Test;

public class TestCase {
@Test
public void test() {}
}

I had a the same exception when running the test task of groovy plugin. Removing guava 15.0 from the classpath of the test task solved the problem for me as a temporary workaround.

project(":projectName") {

  apply plugin: 'groovy'

  (...)

  /*
    Workaround for: http://issues.gradle.org/browse/GRADLE-2962
    Last reviewed on 1 Dec 2013.
  */
  test.doFirst {
    classpath -= fileTree(dir: "$dirWithGuavaJar", include: "guava*.jar")
  }
}

Please note that the workaround causes fallback to guava used by gradle 1.9, that is, 14.0.1 (source: Gradle Forums topic; link above). You cannot use newer version of Guava using this workaround.

This bug was confirmed as a regression:
<quote>
Peter Niederwieser (Core Dev):
This passes with 1.7/1.8 but fails with 1.9. Could be related to our upgrade from guava to guava-jdk5:14.0.1, which might have introduced a problem or surfaced an existing one.
</quote>

Should this issue be fixed faster than others because it's a regression? I see that it's not assigned to anyone. I think the bug tracker should have the flag "regression" and mention version introducing issues.

I've noticed issues with duplicate guava classes in versions prior to 1.10 as well (for example: this function being present in Guava 12 and onwards, which causes exceptions when gradle 1.8 loads guava 11: https://code.google.com/p/guava-libraries/source/browse/guava/src/com/google/common/base/Objects.java#219). This issue could just be manifesting in more ways with the update to guava-jdk5.

That being said, I'm currently running off gradle 1.10 and hurting everywhere when trying to use libraries that depend on the latest versions of Guava. If there's a good way to exclude specific versions of packages at runtime, I would love to know it. A quick peek into the source code suggests this might not be the case: https://github.com/gradle/gradle/blob/master/subprojects/core/src/main/groovy/org/gradle/process/internal/child/WorkerProcessClassPathProvider.java#L69