From 2edc1898b10c27803fea9a7372257d17434d3c6a Mon Sep 17 00:00:00 2001 From: Jeroen Meulemeester Date: Thu, 10 Dec 2015 22:11:21 +0100 Subject: [PATCH] Add proper unit tests for double-checked-locking pattern --- double-checked-locking/pom.xml | 5 + .../doublechecked/locking/Inventory.java | 11 ++ .../doublechecked/locking/InventoryTest.java | 110 ++++++++++++++++++ 3 files changed, 126 insertions(+) create mode 100644 double-checked-locking/src/test/java/com/iluwatar/doublechecked/locking/InventoryTest.java diff --git a/double-checked-locking/pom.xml b/double-checked-locking/pom.xml index 7ad651339..9b87d6859 100644 --- a/double-checked-locking/pom.xml +++ b/double-checked-locking/pom.xml @@ -12,5 +12,10 @@ junit test + + org.mockito + mockito-core + test + diff --git a/double-checked-locking/src/main/java/com/iluwatar/doublechecked/locking/Inventory.java b/double-checked-locking/src/main/java/com/iluwatar/doublechecked/locking/Inventory.java index b51e000a7..0a17ac13d 100644 --- a/double-checked-locking/src/main/java/com/iluwatar/doublechecked/locking/Inventory.java +++ b/double-checked-locking/src/main/java/com/iluwatar/doublechecked/locking/Inventory.java @@ -1,6 +1,7 @@ package com.iluwatar.doublechecked.locking; import java.util.ArrayList; +import java.util.Collections; import java.util.List; import java.util.concurrent.locks.Lock; import java.util.concurrent.locks.ReentrantLock; @@ -38,4 +39,14 @@ public class Inventory { } return false; } + + /** + * Get all the items in the inventory + * + * @return All the items of the inventory, as an unmodifiable list + */ + public final List getItems() { + return Collections.unmodifiableList(items); + } + } diff --git a/double-checked-locking/src/test/java/com/iluwatar/doublechecked/locking/InventoryTest.java b/double-checked-locking/src/test/java/com/iluwatar/doublechecked/locking/InventoryTest.java new file mode 100644 index 000000000..1bc43263f --- /dev/null +++ b/double-checked-locking/src/test/java/com/iluwatar/doublechecked/locking/InventoryTest.java @@ -0,0 +1,110 @@ +package com.iluwatar.doublechecked.locking; + +import org.junit.After; +import org.junit.Before; +import org.junit.Test; +import org.mockito.ArgumentCaptor; + +import java.io.PrintStream; +import java.util.List; +import java.util.concurrent.ExecutorService; +import java.util.concurrent.Executors; +import java.util.concurrent.TimeUnit; + +import static junit.framework.Assert.assertTrue; +import static junit.framework.TestCase.assertEquals; +import static org.junit.Assert.assertNotNull; +import static org.mockito.Mockito.mock; +import static org.mockito.Mockito.times; +import static org.mockito.Mockito.verify; +import static org.mockito.Mockito.verifyNoMoreInteractions; + +/** + * Date: 12/10/15 - 9:34 PM + * + * @author Jeroen Meulemeester + */ +public class InventoryTest { + + /** + * The mocked standard out {@link PrintStream}, used to verify a steady increasing size of the + * {@link Inventory} while adding items from multiple threads concurrently + */ + private final PrintStream stdOutMock = mock(PrintStream.class); + + /** + * Keep the original std-out so it can be restored after the test + */ + private final PrintStream stdOutOrig = System.out; + + /** + * Inject the mocked std-out {@link PrintStream} into the {@link System} class before each test + */ + @Before + public void setUp() { + System.setOut(this.stdOutMock); + } + + /** + * Removed the mocked std-out {@link PrintStream} again from the {@link System} class + */ + @After + public void tearDown() { + System.setOut(this.stdOutOrig); + } + + /** + * The number of threads used to stress test the locking of the {@link Inventory#addItem(Item)} + * method + */ + private static final int THREAD_COUNT = 8; + + /** + * The maximum number of {@link Item}s allowed in the {@link Inventory} + */ + private static final int INVENTORY_SIZE = 1000; + + /** + * Concurrently add multiple items to the inventory, and check if the items were added in order by + * checking the stdOut for continuous growth of the inventory. When 'items.size()=xx' shows up out + * of order, it means that the locking is not ok, increasing the risk of going over the inventory + * item limit. + */ + @Test(timeout = 10000) + public void testAddItem() throws Exception { + // Create a new inventory with a limit of 1000 items and put some load on the add method + final Inventory inventory = new Inventory(INVENTORY_SIZE); + final ExecutorService executorService = Executors.newFixedThreadPool(THREAD_COUNT); + for (int i = 0; i < THREAD_COUNT; i++) { + executorService.execute(() -> { + while (inventory.addItem(new Item())) ; + }); + } + + // Wait until all threads have finished + executorService.shutdown(); + executorService.awaitTermination(5, TimeUnit.SECONDS); + + // Check the number of items in the inventory. It should not have exceeded the allowed maximum + final List items = inventory.getItems(); + assertNotNull(items); + assertEquals(INVENTORY_SIZE, items.size()); + + // Capture all stdOut messages ... + final ArgumentCaptor stdOutCaptor = ArgumentCaptor.forClass(String.class); + verify(this.stdOutMock, times(INVENTORY_SIZE)).println(stdOutCaptor.capture()); + + // ... verify if we got all 1000 + final List values = stdOutCaptor.getAllValues(); + assertEquals(INVENTORY_SIZE, values.size()); + + // ... and check if the inventory size is increasing continuously + for (int i = 0; i < values.size(); i++) { + assertNotNull(values.get(i)); + assertTrue(values.get(i).contains("items.size()=" + (i + 1))); + } + + verifyNoMoreInteractions(this.stdOutMock); + } + +} \ No newline at end of file