executor.shutdown();

        // Then - No unexpected exceptions
        assertTrue(exceptions.isEmpty(), "No unexpected exceptions should occur");
    }

    /**
     * Test that CopyOnWriteArrayList prevents ConcurrentModificationException.
     */
    @Test
    public void testNoConcurrentModificationException() throws Exception {
        // Given

   * @param exceptionType the exception type that triggers use of {@code fallback}. The exception
   *     type is matched against the input's exception. "The input's exception" means the cause of
   *     the {@link ExecutionException} thrown by {@code input.get()} or, if {@code get()} throws a
   *     different kind of exception, that exception itself. To avoid hiding bugs and other

        assertFalse(component.isCloseCalled());

        try {
            failingFactory.destroyObject(pooledObject);
            fail("Should throw exception from close()");
        } catch (Exception e) {
            // Expected - exception should propagate from close()
            assertTrue(e.getMessage().contains("Intentional close failure"));
        }

        // Verify close was attempted

    void testExceptionHierarchy() {
        // When
        RuntimeCIFSException exception = new RuntimeCIFSException("Test");

        // Then
        assertTrue(exception instanceof RuntimeException);
        assertTrue(exception instanceof Exception);
        assertTrue(exception instanceof Throwable);
    }

    @Test
    @DisplayName("Should support exception chaining")

{* ../../docs_src/handling_errors/tutorial002_py39.py hl[14] *}

## Install custom exception handlers { #install-custom-exception-handlers }

You can add custom exception handlers with <a href="https://www.starlette.dev/exceptions/" class="external-link" target="_blank">the same exception utilities from Starlette</a>.

Let's say you have a custom exception `UnicornException` that you (or a library you use) might `raise`.

            List<Exception> exceptions = result.getResolutionErrors(dependency);
            for (Exception e : exceptions) {
                msg.append("\t").append(e.getMessage()).append(System.lineSeparator());
            }
        }

        for (Exception exception : result.getCollectionErrors()) {
            msg.append(exception.getMessage()).append(System.lineSeparator());

     *
     * @param level the severity level of the message
     * @param message the message to be logged
     * @param error the associated exception, or null if not applicable
     */
    void log(@Nonnull Level level, @Nonnull String message, @Nullable Throwable error);

    /**
     * Logs a debug message without an associated exception.
     *

         * @param request the request data
         * @param exceptionList the list of exceptions that occurred during retries
         */
        void onRequestEnd(FaultTolerantClient client, RequestData request, List<Exception> exceptionList);

        /**
         * Called when an exception occurs during a request attempt.
         *
         * @param client the fault-tolerant client

                    conn.connect();
                    successCount.incrementAndGet();
                } catch (Exception e) {
                    synchronized (exceptions) {
                        exceptions.add(e);
                    }
                    failureCount.incrementAndGet();
                } finally {
                    doneLatch.countDown();
                }

        return unresolvedDependencies;
    }

    @Override
    public List<Exception> getCollectionErrors() {
        return collectionErrors;
    }

    public void setCollectionErrors(List<Exception> exceptions) {
        if (exceptions != null) {
            this.collectionErrors = exceptions;
        } else {
            this.collectionErrors = new ArrayList<>();
        }
    }