private static void verifyMainClass(Class<?> mainClass) throws Exception {
        final Object instanceObject = mainClass.newInstance();
        assertEquals("org.embulk.plugin.jar.ExampleJarSpiV0", instanceObject.getClass().getName());
        assertEquals("foobar", ((Callable) instanceObject).call());

        final Object dependencyInstance = ((Supplier) instanceObject).get();
        assertEquals("org.embulk.plugin.jar.ExampleDependencyJar", dependencyInstance.getClass().getName());
        assertEquals("hoge", ((Callable) dependencyInstance).call());
    }
Test cases in this class depend on JARs built by "test-helpers" project.

See "deployJarsForEmbulkTestMavenPlugin" task in test-helpers/build.gradle for more details
embulk-core/src/test/java/org/embulk/plugin/jar/TestJarPluginLoader.java