org.apache.flink.testutils.junit

Class SharedObjects

java.lang.Object

org.junit.rules.ExternalResource

org.apache.flink.testutils.junit.SharedObjects

All Implemented Interfaces:

org.junit.rules.TestRule

@NotThreadSafe
public class SharedObjects
extends org.junit.rules.ExternalResource

This rule allows objects to be used both in the main test case as well as in UDFs by using serializable SharedReferences. Usage:

     @Rule
     public final SharedObjects sharedObjects = SharedObjects.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 Summary

Modifier and Type	Method and Description
<T> SharedReference<T>	add(T object) Adds a new object to this SharedObjects.
protected void	after()
protected void	before()
static SharedObjects	create() Creates a new instance.
boolean	equals(Object o)
int	hashCode()

Methods inherited from class org.junit.rules.ExternalResource

apply

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait

Method Detail

create

public static SharedObjects 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.

before

protected void before()
               throws Throwable

Overrides:

before in class org.junit.rules.ExternalResource

Throws:

Throwable

after

protected void after()

Overrides:

after in class org.junit.rules.ExternalResource

equals

public boolean equals(Object o)

Overrides:

equals in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object