1. A relevance test system for executing one or a combination of test scenarios, each test scenario respectively being configured to selectively exercise components of a relevance service, the system comprising: the relevance service configured to provide a program interface for receiving relevance service requests via a network, wherein each relevance service request is associated with a user, and the relevance service is configured to process the relevance service request by identifying a set of promotions that are relevant to the user using components of the relevance service in a sequence, wherein the components include predefined filtering algorithms and filtering rules; and a relevance test service platform comprising a relevance test driver layer, wherein the relevance test service platform is operable to interact with the relevance service using the program interface via the network using at least one relevance test driver from the relevance test driver layer, the relevance test service platform being configured to perform operations comprising: receiving test configuration data describing a test scenario representing processing of a test relevance service request on behalf of at least one model user, wherein: the test relevance service request is submitted as a direct invocation of the program interface of the relevance service by the at least one relevance test driver from the relevance test driver layer; the test configuration data includes filtering workflow parameters defining the test scenario as one of (a) an end-to-end test of the components of the relevance service in the sequence or (b) a directed test of a selected one or more components of the relevance service; the test configuration data further includes model user input parameters describing the model user and model promotion input parameters describing one or more promotion attributes for selection by the relevance service of a set of promotions potentially available to the model user, wherein the model user input parameters comprise at least a user email address, a user location, a user gender, data representing user consumer behavior, and data representing user-personalized themes and preferences; and the test configuration data further includes a first output expected to be generated by the relevance service while processing the test relevance service request for the end-to-end test or the directed test; and in response to receiving the test configuration data: generating the test relevance service request based on the test configuration data; submitting the test relevance service request to the relevance service using the relevance service program interface; receiving a second output generated by the relevance service while processing the test relevance service request; and analyzing the test scenario based in part on comparing the second output to the first output.