Package org.apache.flink.testutils.junit

Class SharedObjectsExtension

  • All Implemented Interfaces:
    org.junit.jupiter.api.extension.AfterEachCallback, org.junit.jupiter.api.extension.BeforeEachCallback, org.junit.jupiter.api.extension.Extension
    @NotThreadSafe
public class SharedObjectsExtension
extends Object
implements org.junit.jupiter.api.extension.BeforeEachCallback, org.junit.jupiter.api.extension.AfterEachCallback
    This rule allows objects to be used both in the main test case as well as in UDFs by using serializable SharedReferences. Usage: 
    
    @RegisterExtension
     public final SharedObjectsExtension sharedObjects = SharedObjectsExtension.create();

    @Test
     public void test() throws Exception {
         StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();
        SharedReference<Queue<Long>> listRef = sharedObjects.add(new ConcurrentLinkedQueue<>());
         int n = 10000;
         env.setParallelism(100);
         env.fromSequence(0, n).map(i -> listRef.get().add(i));
         env.execute();
         assertEquals(n + 1, listRef.get().size());
         assertEquals(
                 LongStream.rangeClosed(0, n).boxed().collect(Collectors.toList()),
                 listRef.get().stream().sorted().collect(Collectors.toList()));
     }

    The main idea is that shared objects are bound to the scope of a test case instead of a class. That allows us to:

    • Avoid all kinds of static fields in test classes that only exist since all fields in UDFs need to be serializable.
    • Hopefully make it easier to reason about the test setup
    • Facilitate to share more test building blocks across test classes.
    • Fully allow tests to be rerun/run in parallel without worrying about static fields

    Note that since the shared objects are accessed through multiple threads, they need to be thread-safe or accessed in a thread-safe manner.

    • Method Detail

      • create

        public static SharedObjectsExtension create()
        Creates a new instance. Usually that should be done inside a JUnit test class as an instance-field annotated with Rule.

      • add

        public <T> SharedReference<T> add​(T object)
        Adds a new object to this SharedObjects. Although not necessary, it is recommended to only access the object through the returned SharedReference.

      • beforeEach

        public void beforeEach​(org.junit.jupiter.api.extension.ExtensionContext context)
                throws Exception
        Specified by:
        beforeEach in interface org.junit.jupiter.api.extension.BeforeEachCallback
        Throws:
        Exception

      • afterEach

        public void afterEach​(org.junit.jupiter.api.extension.ExtensionContext context)
               throws Exception
        Specified by:
        afterEach in interface org.junit.jupiter.api.extension.AfterEachCallback
        Throws:
        Exception

      • hashCode

        public int hashCode()
        Overrides:
        hashCode in class Object