docMap.put("mimetype", mimeType);
            assertFalse("Should not support " + mimeType, thumbnailGenerator.isTarget(docMap));
        }
    }

    @Test
    public void test_concurrentOperations() throws InterruptedException {
        // Test thread safety with concurrent operations
        final int threadCount = 10;
        Thread[] threads = new Thread[threadCount];

        // with message "Failed to write a userDict file." - this is covered by
        // the constructor's exception handling implementation
    }

    @Test
    public void test_concurrent_operations() {
        // Test concurrent read operations
        protwordsFile.reload(null);

        // Multiple reads should work fine
        OptionalEntity<ProtwordsItem> item1 = protwordsFile.get(1);