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diff --git a/src/test/java/org/apache/commons/lang3/concurrent/CallableBackgroundInitializerTest.java b/src/test/java/org/apache/commons/lang3/concurrent/CallableBackgroundInitializerTest.java
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+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.commons.lang3.concurrent;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+import java.util.concurrent.Callable;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
+
+import org.apache.commons.lang3.AbstractLangTest;
+import org.junit.jupiter.api.Test;
+
+/**
+ * Test class for {@code CallableBackgroundInitializer}
+ */
+public class CallableBackgroundInitializerTest extends AbstractLangTest {
+    /** Constant for the result of the call() invocation. */
+    private static final Integer RESULT = Integer.valueOf(42);
+
+    /**
+     * Tries to create an instance without a Callable. This should cause an
+     * exception.
+     */
+    @Test()
+    public void testInitNullCallable() {
+        assertThrows(NullPointerException.class, () -> new CallableBackgroundInitializer<>(null));
+    }
+
+    /**
+     * Tests whether the executor service is correctly passed to the super
+     * class.
+     */
+    @Test
+    public void testInitExecutor() throws InterruptedException {
+        final ExecutorService exec = Executors.newSingleThreadExecutor();
+        final CallableBackgroundInitializer<Integer> init = new CallableBackgroundInitializer<>(
+                new TestCallable(), exec);
+        assertEquals(exec, init.getExternalExecutor(), "Executor not set");
+        exec.shutdown();
+        exec.awaitTermination(1, TimeUnit.SECONDS);
+    }
+
+    /**
+     * Tries to pass a null Callable to the constructor that takes an executor.
+     * This should cause an exception.
+     */
+    @Test
+    public void testInitExecutorNullCallable() throws InterruptedException {
+        final ExecutorService exec = Executors.newSingleThreadExecutor();
+        try {
+            assertThrows(NullPointerException.class, () -> new CallableBackgroundInitializer<Integer>(null, exec));
+        } finally {
+            exec.shutdown();
+            exec.awaitTermination(1, TimeUnit.SECONDS);
+        }
+
+    }
+
+    /**
+     * Tests the implementation of initialize().
+     *
+     * @throws Exception so we don't have to catch it
+     */
+    @Test
+    public void testInitialize() throws Exception {
+        final TestCallable call = new TestCallable();
+        final CallableBackgroundInitializer<Integer> init = new CallableBackgroundInitializer<>(
+                call);
+        assertEquals(RESULT, init.initialize(), "Wrong result");
+        assertEquals(1, call.callCount, "Wrong number of invocations");
+    }
+
+    /**
+     * A test Callable implementation for checking the initializer's
+     * implementation of the initialize() method.
+     */
+    private static class TestCallable implements Callable<Integer> {
+        /** A counter for the number of call() invocations. */
+        int callCount;
+
+        /**
+         * Records this invocation and returns the test result.
+         */
+        @Override
+        public Integer call() {
+            callCount++;
+            return RESULT;
+        }
+    }
+}