void testGetInstanceWithoutSetInstance() {
        // Test getInstance when no instance has been set
        // Should default to System.err
        LogStream instance = LogStream.getInstance();
        assertNotNull(instance);

        // Getting instance again should return the same instance
        LogStream instance2 = LogStream.getInstance();
        assertSame(instance, instance2);
    }

    @Test

    // Use reflection to reset the singleton instance between tests
    @BeforeEach
    @AfterEach
    void resetSingleton() {
        try {
            Field instance = SingletonContext.class.getDeclaredField("INSTANCE");
            instance.setAccessible(true);
            instance.set(null, null);
        } catch (NoSuchFieldException | IllegalAccessException e) {

        byte[] buffer = new byte[] { (byte) 0xff, (byte) 0xff, 0, 0, 0, 0, 0, 0 };
        SmbComWriteAndXResponse instance = new SmbComWriteAndXResponse(config);

        // When
        int result = instance.readParameterWordsWireFormat(buffer, 0);

        // Then
        assertEquals(8, result);
        assertEquals(0xffffL, instance.getCount());
    }

    /**
     * Test of readParameterWordsWireFormat with zero count
     */

But we want to be able to parameterize that fixed content.

## A "callable" instance { #a-callable-instance }

In Python there's a way to make an instance of a class a "callable".

Not the class itself (which is already a callable), but an instance of that class.

To do that, we declare a method `__call__`:

{* ../../docs_src/dependencies/tutorial011_an_py39.py hl[12] *}

     * <p>
     * If a root package is specified at instance construction, the specified class name is interpreted as a relative name from the root package.
     * </p>
     *
     * @param className the class name
     * @return <code>true</code> if the class file exists in the resources handled by this instance
     */
    boolean isExistClass(final String className);

	<component name="crawler" class="org.codelibs.fess.crawler.Crawler" instance="prototype" >
	</component>

	<!-- Crawler Thread -->
	<component name="crawlerThread" class="org.codelibs.fess.crawler.CrawlerThread" instance="prototype" >
	</component>

	<!-- Entity -->
	<component name="accessResult" class="org.codelibs.fess.crawler.entity.AccessResultImpl" instance="prototype" >
	</component>

Pero queremos poder parametrizar ese contenido fijo.

## Una *instance* "callable"

En Python hay una forma de hacer que una instance de una clase sea un "callable".

No la clase en sí (que ya es un callable), sino una instance de esa clase.

Para hacer eso, declaramos un método `__call__`:

{* ../../docs_src/dependencies/tutorial011_an_py39.py hl[12] *}

   * intern(a)} is permitted to return one instance now and a different instance later if the
   * original interned instance was garbage-collected.
   *
   * <p><b>Warning:</b> do not use with mutable objects.
   *
   * @throws NullPointerException if {@code sample} is null
   */
  E intern(E sample);

	<component name="internalHttpClient" class="org.codelibs.fess.crawler.client.http.HcHttpClient"
		instance="prototype">
		<property name="connectionTimeout">15000</property>
		<property name="soTimeout">30000</property>
	</component>
	<component name="httpClient"
		class="org.codelibs.fess.crawler.client.FaultTolerantClient" instance="prototype">
		<property name="crawlerClient">internalHttpClient</property>

	</component>

	<!-- Jobs -->
	<component name="crawlJob" class="org.codelibs.fess.job.CrawlJob" instance="prototype">
	</component>
	<component name="suggestJob" class="org.codelibs.fess.job.SuggestJob" instance="prototype">
	</component>
	<component name="aggregateLogJob" class="org.codelibs.fess.job.AggregateLogJob" instance="prototype">
	</component>