Before we go in to more detail on testing usability, why don't we recap a few of the key things that you learned in course two. So first of all, this idea of simplicity is important, yet a lot more complicated if you're actually having the job of creating simplicity. So to achieve simplicity, we need to get focused, to get focused, we need to have confidence that we understand what's really important to the user, and to have that confidence, we need the understanding that only comes with the kind of validated learning that you now know how to achieve through the tools that you've learned in the course. We learned about a systematic view of user cognition and usability through Donald Norman's 7 Steps framework. So user's move from a goal to this feed forward loop of figuring out how they're going to accomplish that goal with your tool, and then you have a feedback loop where they assess what you're telling them against what they wanted. And we need to both think through this before the fact and then test against this idea after the fact to see if we're achieving good usability for the user. We learned a vocabulary of how to talk about the specifics of our executions around usability. So we learned about signifiers, affordances, constraints, the process of feedback, and how to keep an eye out for identifying and pairing mappings that users have about how things work, especially in the software world with the tasks that we're going to put in front of them. And how to pair those two things, so that we don't create novel affordances or novel signifiers that are confusing to the user. Instead we stick to well established behavioral patterns and mappings. And we learn that the way that we get to those good mappings and those appropriate signifiers and affordances is that we make sure that we come into this process with nice strong narrative about what the user really wants to achieve, and not crappy narrative like the red button story where we kind of just say, well, the user wants this because they want it. We learned how to grind through that and move from personas, to problem scenarios, to user stories, making sure that we're anchoring our execution in a strong, testable proposition, so that our primary input into the design process is vivid, validated, testable narrative. And we learned how to use that process in reverse, so that if we have a feature that's not usable or seems to be irrelevant to users, we know that we can look back through, how did we implement the narrative, to, what did we think was the problem we were solving? Why did we think it was compelling? And who was this person, again? And if you're doing this a lot, totally fine. It's completely normal. It's normal to spend a lot of time assessing usability after the fact. Nobody gets it perfect 100% of the time. Succesful teams recognize that fact and they are constantly looking back at what they did and how the users are reacting to it. We talked about the significance of this third clause on the user story and why it's so important. It's so important because this is where on a story by story basis, so on an interaction by interaction basis, we're creating strong testable views of what we think we want to achieve for the user. And we've talked a lot about this in the last module. But we learned that when we're testing, we want to make sure that we're focused on testing this, and that we control for motivation by establishing motivation and creating a set of tasks for the user, not by doing both at the same time. So for example, if our software paints walls online, then we don't want to ask the user, hey, would you like to paint a wall? What color do you want this wall to be. We just tell them, hey, could you show me how you'd paint this wall yellow? And we're going to talk a lot about how to do that over the balance of this course. We talked about phase appropriate usability testing and the importance of getting at this early. And we talked about this test plan template that is really accessible. Anybody can use it with a small amount of practice. So over the balance of the module here, we're going to use that test plan template as a focal point. And we're going to go through the elements of it. And you're going to learn how to actually go through, create, run, and then act on the results of usability testing over the balance of this module here. So we've recapped a few of the key ideas about usability here. If any of those are fuzzy for you, you can go back to the lesson resources or back to the module on usability sprints in course two.