[CentOS] HERE document in docker script file

I am trying to use a HERE document in a docker script file to generate a text file but must be doing something wrong since I get a warning message that I did not expect:

EOF: line 6: warning: here-document at line 0 delimited by end-of-file (wanted `EOF')

This is the sample script I am testing in my docker file:

RUN bash -c "$(/bin/echo -e "cat << 'EOF' | tee -a /test.txt \
    \n<test> \
    \n  someting here \
    \n  something else here \
    \n</test>")" \
EOF

Can anyone see what is wrong in the above statement?

Thanks.