After upgrade readyAPI 1.9 to the higher version, pop up error "java.lang.NoClassDefFoundError:org/openxmlformats/schemas/spreadsheetml/x2006/main/CTExtensionList".

solution:
replace "poi-ooxml-schemas-3.12.jar" with "ooxml-schemas-1.1.jar" in ReadyAPI lib folder.

official website clarifies the issue http://poi.apache.org/help/faq.html#faq-N10025