Fix "junitvmwatcherXXX.properties could not be found" during grails unit test

Recently, I forked grails-core to fix the GRAILS-5876. But, when I modified and ran "gradlew testSingleMockUtils", I got a java.io.FileNotFoundException:

java.io.FileNotFoundException: D:\grails\grails-core\junitvmwatcher476409304.properties(no such file or directory)

Compile phase (sources compile and tests compile) was ok, the exception was thrown from the Unit Test phase, and the unit test didn't be launched at all. I tried another build approach, "ant -Dtest=MockUtils test", and got the same exception.
This is very confusing, beacause I launched unit tests successfully under grails 1.2. Google could not give me any suggest this time. Taking a close look at the output on the screen, I found some messages which showed the memory was not enough for running unit tests. That is it!
I compared the unit-test.xml in my local git repository with the one in grails 1.2 dist, and found there was some diffrence in the target "run-test" between these two files:

• my local git repository:
  

  <target name="run-test" depends="defineTestingScope, build-test,-jar-app-files" unless="_skipTests_">
  <delete dir="${grails.test.reports}" />
  <mkdir dir="${grails.test.reports}" />
  <echo>Test being run ${test} from ${grails.test.build}</echo>
  <junit fork="true" forkmode="perBatch" clonevm="true" printsummary="on">
      <!-- only fork VMs as needed -->
      <sysproperty key="grails.cli.testing" value="true"/>
      <jvmarg line="-server -Dgroovy.grails.joint=${groovy.grails.joint} ${args.memory} ${args.debug}"/>

• grails 1.2 dist:

  <target name="run-test" depends="defineTestingScope, build-test,-jar-app-files" unless="_skipTests_">
  <delete dir="${grails.test.reports}" />
  <mkdir dir="${grails.test.reports}" />
  <echo>Test being run ${test} from ${grails.test.build}</echo>
  <junit fork="true" forkmode="perBatch" clonevm="true" printsummary="on">
      <!-- only fork VMs as needed -->
      <sysproperty key="grails.cli.testing" value="true"/>
      <jvmarg value="-server" />
     <jvmarg value="-Xmx1G" />
     <jvmarg value="-Xms256m" />
     <jvmarg value="-XX:MaxPermSize=256m"/>
     <jvmarg value="-Dgroovy.grails.joint=${groovy.grails.joint}" />
...

The solution is obvious. Replacing the last statement in the former build script with the last 5 statements in the latter, I could run the unit test successfully again. Now, let's fix the gradle build script. Open the unit-test.gradle, and search the following statement:

options.forkOptions.jvmArgs = ["-server", "-Xmx1500m", "-Xms256m", "-XX:MaxPermSize=256m", "-Dgroovy.grails.joint=true"]

Change "-Xmx1500m" to "-Xmx1G", and save the file. Then you should run "gradlew testSingleMockUtils" successfully.
There are other reasons can cause "junitvmwatcherXXX.properties could not be found", you could get some advices from google using the key works "ant junitvmwatcherXXX.properties".