1. A testing system, comprising: at least one computing device including a hardware processor configured to implement a plurality of services including: an interceptor service configured to perform an intercept of a request to a production system; and a testing service configured to process the intercepted request by: causing a candidate request to be processed by a candidate system operating a candidate software system to be validated; causing a control request to be processed by a control system operating a control software systems that is used for validating the candidate software system, wherein the candidate request and the corresponding control request are based at least in part on the intercepted request; receiving, in response to the candidate request, a candidate response from the candidate software system; receiving, in response to the corresponding control request, a control response from the control software system; and comparing a candidate tree structure of the candidate response to a corresponding control tree structure of the control response to obtain one or more candidate test differences, the comparing comprising: detecting a complexity of a sub-tree structure of the candidate tree structure or a complexity of a sub-tree structure of the corresponding control tree structure; pairing nodes of the sub-tree structure of the candidate tree structure with nodes of the sub-tree structure of the corresponding control tree structure using tags of the nodes of the candidate tree structure and tags of the nodes of the corresponding control tree structure if the detected complexity is lower than a threshold; and if the detected complexity is greater than the threshold: pairing nodes of the sub-tree structure of the candidate tree structure with nodes of the sub-tree structure of the corresponding control tree structure using structural information of the sub-tree structure of the candidate tree structure and structural information of the sub-tree structure of the corresponding control tree structure and using content of the nodes of the sub-tree structure of the candidate tree structure and content of the nodes of the sub-tree structure of the corresponding control tree structure; and determining if the sub-tree structure of the candidate tree structure is of a type of sub-tree structure for which a corresponding matching process is defined; and performing the corresponding matching process to compare the sub-tree structure of the candidate tree structure with the sub-tree structure of the corresponding control tree structure.