void constructor_invalidMode_throws() {
        SmbFile file = mock(SmbFile.class);
        assertThrows(IllegalArgumentException.class, () -> new SmbRandomAccessFile(file, "badmode"));
    }

    @Test
    @DisplayName("open(): acquires and releases handle (no I/O)")
    void open_acquiresAndReleasesHandle() throws Exception {

import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.Channel;
import java.nio.channels.FileChannel;
import java.nio.channels.FileChannel.MapMode;

import org.codelibs.core.exception.IORuntimeException;

/**
 * Utility for {@link Channel}.
 *
 * Author: koichik
 */
public abstract class ChannelUtil {

    /**
     * Do not instantiate.

					req.Header.Set("authorization", req.Header.Get("authorization")+"a")
					// Setting an invalid Content-MD5 to force a Md5 Mismatch error.
					// Used in tesr case 7.
				case BadMD5:
					req.Header.Set("Content-MD5", "badmd5")
				}

				// invoke the PutObjectPart HTTP handler.
				apiRouter.ServeHTTP(rec, req)

				// validate the error response.
				want := getAPIError(test.expectedAPIError)