Support for jpy integration junit tests

Partial deephaven#430

py/jpy-integration/build.gradle

@@ -110,6 +110,50 @@ Task pythonToJava = tasks.create 'unittestPythonToJava', {
 }
 
 if (!PyEnv.pythonEnabled(project)) {
+  Closure<TaskProvider<Task>> gradleTestInDocker = { String taskName, SourceSet sourceSet ->
+
+    def gradleWrapper = tasks.register("${taskName}GradleInit", Wrapper.class) { wrapper ->
+      wrapper.scriptFile "${buildDir}/template-project/gradlew"
+      wrapper.jarFile "${buildDir}/template-project/gradle/wrapper/gradle-wrapper.jar"
+    }
+    return Docker.registerDockerTask(project, taskName) {
+      copyIn {
+        dependsOn gradleWrapper
+        from ("${buildDir}/template-project") {
+          into 'project'
+        }
+        from(project.file('src/javaToPython/build.gradle.template')) {
+          into 'project'
+          rename { file -> 'build.gradle' }
+        }
+        from (sourceSet.runtimeClasspath) {
+          into 'classpath'
+        }
+        from (sourceSet.output.getClassesDirs()) {
+          into 'classes'
+        }
+      }
+      dockerfile {
+        // base image with default java, python, wheels
+        from 'deephaven/runtime-base'
+
+        // set up the project
+        copyFile 'project', '/project'
+        workingDir '/project'
+        // run once with no actual classes, so that gradle is preinstalled and cached
+        runCommand '/project/gradlew'
+        copyFile 'classpath', '/classpath'
+        copyFile 'classes', '/classes'
+      }
+      entrypoint = ['/project/gradlew', 'test', '--info']
+      containerOutPath = '/project/build/test-results/test/'
+      copyOut {
+        into "${buildDir}/test-results/${taskName}"
+      }
+    }
+  }
+  testJavaToPython.dependsOn gradleTestInDocker('java-to-python-test', sourceSets.javaToPython)
+
 //  Task testTask = venvTest.javaTest(project, "java-to-python-test-${pv.name}", installWheels, sourceSets.javaToPython)
 //  testJavaToPython.dependsOn testTask
 

py/jpy-integration/src/javaToPython/build.gradle.template

@@ -0,0 +1,18 @@
+plugins {
+    id 'java-library'
+}
+
+// Classpath is already built, just need to pass to the test task
+test.classpath = fileTree('/classpath/').plus(files('/classpath'))
+test.testClassesDirs = files('/classes')
+
+test.systemProperties([
+        'jpy.jpyLib':'/usr/local/lib/python3.7/dist-packages/jpy.cpython-37m-x86_64-linux-gnu.so',
+        'jpy.jdlLib':'/usr/local/lib/python3.7/dist-packages/jdl.cpython-37m-x86_64-linux-gnu.so',
+        'jpy.pythonLib':'/usr/lib/x86_64-linux-gnu/libpython3.7m.so.1.0',
+        // Cleaning up on a dedicated thread has some issues when there is frequent starting
+        // and stopping of the python virtual environment. We'll rely on cleaning up inline
+        // when necessary.
+        'PyObject.cleanup_on_thread':'false',
+//        'jpy.debug':'true'
+])