Summative AssessmentThis summative assessment would be used in an English classroom to assess student's mastery to constructing an argument.
Validity is assessed by creating learning goals and objectives which are aligned to national standards and aligning both lessons, formative assessment questions, and the summative assessment.
Reliability is assessed using previous assessments from writing task. As a teacher, one should be able notice variances in student writing and word choice based off discussion task and other writing task.
Security is hard to guarantee on writing task but I would take precautions like using a search engine to ensure students didn't copy and paste off the internet.