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Forgive me for being vague and brief, but I've been trying to test my UIs for the last year or so and this is what I've come up with. I've found the ideas in G

Forgive me for being vague and brief, but I've been trying to test my UIs for the last year or so and this is what I've come up with. I've found the ideas in Gary Bernhardt's talk, Boundaries (1), to be very helpful in figuring out how to test interactive web UIs. The basic idea is that DOM manipulation can be an "imperative shell" with as little logic and as few conditionals as possible. Derive the state of your UI component with separate functions and methods that return plain values (a "functional core"), and write tests for those because testing for values is easy. So no, don't test for the presence of classes and IDs. Test your imperative shell once, maybe even manually or with an integration test, and that's probably enough. Angular and React both encourage something like this approach, but you don't need those technologies to do it this way. In Backbone, for instance, just try to avoid conditionals and logic in your templates and render methods. If you think your UI piece needs to render with conditionals because it can be in different states, ask yourself if those states are just appearances that can be programmed declaratively with classes and CSS. Also, testing is so much easier when you limit API surface areas. So if you're using a library like Backbone, where models and views both have many methods with many ways they can be called and used, don't give them direct references to each other. I've had some success in having models and views communicate only with a global event bus, which means my objects don't even know about each other. This makes them easier to specify, which makes them easier to test, which usually results in more focused interfaces and responsibilities. (1) https://www.youtube.com/watch?v=yTkzNHF6rMs https://www.youtube.com/watch?v=yTkzNHF6rMs

Chris_Newton 12y ago
I often plan large-scale UI code as three fundamental levels: 1. Model data 2. View data 3. Rendered data The model data comes from whatever underlying data store and business rules you are working with. The view data contains every value you need to render your UI. This typically includes a lot of data taken straight from the model. However, it can also include derived data, perhaps the result of some arithmetic calculation or the outcome of some conditional logic. This is also the level where any view metadata that isn’t persisted in the model lives, for example if you need to keep track of a cursor position, zoom level, contents of a clipboard/kill ring, etc. The rendered data level only applies if you’re creating your UI using a descriptive/declarative system rather than by calling some sort of API. For example, for a web app, the rendered data would be HTML ready to put into the DOM. At this level, I try to keep the logic trivial; you might need some basic conditional or loop logic in the rendering, but the view data is where anything complicated happens, and the rendering logic in something like an HTML template shouldn’t be more complicated than “if (simple boolean value provided by view data) then (version A) else (version B)” or “for each item in (list provided by view data) do (render individual item)”. Ideally, the conversions from model data to view data and from view data to rendered data are pure (as in without side-effects) functions, and therefore in principle they are amenable to automated testing techniques in isolation. For example, it is straightforward to add unit tests that calculated view data do have the expected values for sample model data. In practice, I find automated testing of the view data to rendered data stage has very little value, for two reasons. Firstly, if your rendering stage is basically just filling out templates using view data and the logic is trivial, errors tend to be obvious: a table has no contents, for example, or an entire part of the page disappears. Secondly, my experience is that most of the bugs I find at the rendering level don’t actually originate in the rendering logic. Rather, they tend to be in some accompanying data, such as a CSS stylesheet that didn’t include the right prefixes or got the media queries wrong, or as a bug in the rendering engine itself that is out of your immediate control, such as a browser layout engine bug. Edit: Of course, the above only describes data going one way through the system. Depending on the application, you might also have interactions that update view meta-data, and in anything beyond pure visualisation code you’ll surely have interactions that need to update the model data. This is also amendable to automated testing, as long as you have reasonable separation between (a) the code that does things like validation, constraint checks and eventually state modification at the model and view levels, and (b) whatever event-handling or other code starts the process. In this case, it’s that event-handling or other trigger code that is the part where bugs tend to be either obvious or outside of your immediate control, and you can have unit test suites for everything below. You can also use tools like Selenium to simulate those initial interactions and test in a more end-to-end fashion in real browsers.

Chris_Newton 12y ago

I often plan large-scale UI code as three fundamental levels: 1. Model data 2. View data 3. Rendered data The model data comes from whatever underlying data store and business rules you are working with. The view data contains every value you need to render your UI. This typically includes a lot of data taken straight from the model. However, it can also include derived data, perhaps the result of some arithmetic calculation or the outcome of some conditional logic. This is also the level where any view metadata that isn’t persisted in the model lives, for example if you need to keep track of a cursor position, zoom level, contents of a clipboard/kill ring, etc. The rendered data level only applies if you’re creating your UI using a descriptive/declarative system rather than by calling some sort of API. For example, for a web app, the rendered data would be HTML ready to put into the DOM. At this level, I try to keep the logic trivial; you might need some basic conditional or loop logic in the rendering, but the view data is where anything complicated happens, and the rendering logic in something like an HTML template shouldn’t be more complicated than “if (simple boolean value provided by view data) then (version A) else (version B)” or “for each item in (list provided by view data) do (render individual item)”. Ideally, the conversions from model data to view data and from view data to rendered data are pure (as in without side-effects) functions, and therefore in principle they are amenable to automated testing techniques in isolation. For example, it is straightforward to add unit tests that calculated view data do have the expected values for sample model data. In practice, I find automated testing of the view data to rendered data stage has very little value, for two reasons. Firstly, if your rendering stage is basically just filling out templates using view data and the logic is trivial, errors tend to be obvious: a table has no contents, for example, or an entire part of the page disappears. Secondly, my experience is that most of the bugs I find at the rendering level don’t actually originate in the rendering logic. Rather, they tend to be in some accompanying data, such as a CSS stylesheet that didn’t include the right prefixes or got the media queries wrong, or as a bug in the rendering engine itself that is out of your immediate control, such as a browser layout engine bug. Edit: Of course, the above only describes data going one way through the system. Depending on the application, you might also have interactions that update view meta-data, and in anything beyond pure visualisation code you’ll surely have interactions that need to update the model data. This is also amendable to automated testing, as long as you have reasonable separation between (a) the code that does things like validation, constraint checks and eventually state modification at the model and view levels, and (b) whatever event-handling or other code starts the process. In this case, it’s that event-handling or other trigger code that is the part where bugs tend to be either obvious or outside of your immediate control, and you can have unit test suites for everything below. You can also use tools like Selenium to simulate those initial interactions and test in a more end-to-end fashion in real browsers.