reuseForks=false

[jglick]

Trying to fix #135 (comment) by working around a regression from junit-team/junit4#1517.

[jglick]

FTR there were several things going on, detecting from PCT failures.

First, there was a linkage error from ssh-slaves, which #135 corrects.

This was also triggering a Docker fixture error, corrected in jenkinsci/docker-fixtures#26. Initially was thought to be specific to DooD, but in fact turned out to be reproducible even when Surefire was running on the host.

But then #135 picked up junit-team/junit4#1517 which introduced an error visible only in certain modes, not in individual tests and apparently also not when you run tests in parallel under certain conditions. Seen for example in

V=2.150.3
mvn dependency:get -Dartifact=org.jenkins-ci.main:jenkins-war:$V:war
docker run -ti --rm -v /var/run/docker.sock:/var/run/docker.sock -v $HOME/.m2:/root/.m2 -v /tmp/out:/pct/out -v $HOME/.m2/repository/org/jenkins-ci/main/jenkins-war/$V/jenkins-war-$V.war:/pct/jenkins.war:ro -v $(pwd):/pct/plugin-src -e ARTIFACT_ID=mercurial -e SHARED_DOCKER_SERVICE=true jenkins/pct -mavenProperties maven.test.redirectTestOutputToFile=true:test=InjectedTest,CacheTest,CachingCustomDirSCMTest,CachingSCMTest

or more simply in

mvn test -Dmaven.test.redirectTestOutputToFile=true -Dtest=InjectedTest,CacheTest,CachingCustomDirSCMTest,CachingSCMTest

The JUnit regression was tracked down by bisecting after

diff --git pom.xml pom.xml
index 60f37f8..060942d 100644
--- pom.xml
+++ pom.xml
@@ -18,6 +18,11 @@
       <jenkins.version>2.150.3</jenkins.version>
       <java.level>8</java.level>
       <no-test-jar>false</no-test-jar>
+      <junit.version>4.13-SNAPSHOT</junit.version>
+      <test>InjectedTest,CacheTest,CachingCustomDirSCMTest,ChangelogTest#spacesInPaths[2]</test>
+      <enforcer.skip>true</enforcer.skip>
+      <maven.test.redirectTestOutputToFile>false</maven.test.redirectTestOutputToFile>
+      <surefire.rerunFailingTestsCount>1</surefire.rerunFailingTestsCount>
     </properties>
     
     <developers>
@@ -80,6 +85,11 @@
                 <scope>import</scope>
                 <type>pom</type>
             </dependency>
+            <dependency>
+                <groupId>junit</groupId>
+                <artifactId>junit</artifactId>
+                <version>${junit.version}</version>
+            </dependency>
         </dependencies>
     </dependencyManagement>
     <dependencies>
@@ -169,7 +179,7 @@
         <dependency>
             <groupId>org.jenkins-ci.test</groupId>
             <artifactId>docker-fixtures</artifactId>
-            <version>1.8</version>
+            <version>1.10-SNAPSHOT</version>
             <scope>test</scope>
         </dependency>
         <dependency>

[jglick]

Supposedly junit-team/junit4#1687 (and junit-team/junit4#1691?) planned for JUnit 1.13.2 will render this unnecessary. Still, it seems safest to keep reuseForks=false generally for this plugin. The overhead of a new JVM & class loading is significant even compared to the overhead of JenkinsRule, but these tests are quite slow even for JenkinsRule.

[jglick]

Acc. to junit-team/junit4#1652 (comment) updating to JUnit 4.13.2 would allow this to be reverted, if desired. Not sure it matters much.