String result = purgeThumbnailJob.execute();

        assertEquals("Deleted 0 thumbnail files.", result);
        assertEquals(30L * 24 * 60 * 60 * 1000L, thumbnailManager.getPurgeExpiry());
    }

    // Test execute with successful purge (single file deleted)
    @Test
    public void test_execute_singleFileDeleted() {
        thumbnailManager.setPurgeCallCount(1);