GOOS

TDD

• judging where to set the boundaries of what to test.
• how to eventually cover everything.
• uses Acceptance tests to show incremental progress.
• each acceptance test should have just enough new requirements to force a manageable increase in functionality.
• write a high-level end-to-end test to describe what the system should implements.
• write long unit test names to tell us what a class does.
• extract new classes to tease apart fine-grained aspects of the functionality.
• write lots of little methods to keep each layer of code at a consistent level of abstraction.
• write a rough implementation to prove that we know how to make the code do what's required and then we refactor.
• single responsibility principle is a very effective heuristic for breaking up complexity.
• how we're growing a design from what looks like an unpromising start? alternate, more or less, between adding features and reflecting on - and cleaning up the code that results. we're prepared to defer refactoring code if we're not yet clear what to do, confident that we will take the time when we're ready. In the meantime, keep our code as clean as possible, moving in small increments and using techniques such as null implementation to minimize the time when it's broken.
• makes steady progress by adding a little slices of functionality at a time.
• makes it "working" is not mean that is "finished".
• When we're not sure what to do next or how to get there from here, one way of coping is to scale down the individual changes we make.

Incremental Development

• how to slice up the functionality so that it can be built a little at a time?
  • each slice should be significant and concrete enough so that the team can tell when it's done.
  • each slice should be small enough to be focused on one concept and achievable quickly.

Benefit

• dividing the work into small, coherent chunks helps us manage the development risk.
• we get regular, concrete feedback on the progress we'are making, so we can adjust the plan as the team discovers more about the domain and the technologies.

Walking Skeleton

developing the walking skeleton takes a surprising amount of effort.

• deciding what to do will flush out all sorts of questions about the application and its place in the world.
• the automation of building, packaging, and deploying into a production-like environment will flush out all sorts of technical and organizational questions.

Benefit

• help us understand the requirements well enough to propose and validate a broad-brush system structure.
• it's very important to be able to assess the approach we've chosen and to test our decisions.

Iteration Zero

doing initial analysis, setting up its physical and technical environments, and otherwise getting started. it isn't adding much visible functionality since almost all the work is infrastructure. One important task for iteration zero is to use the walking skeleton to test-drive the initial architecture.

Iteration zero usually brings up project chartering issues as the team looks for criteria to guide its decisions, so the project's sponsors should expect to field some deep questions about its purpose.

Programming by Intention

working backwards from the test helps us focus on what we want the system to do, instead of getting caught up in the complexity of how we will make it work.

One Domain at a Time

keeping the language consistent helps us understand what's significant in this test, with a nice side effect of protecting us when the implementation inevitably changes.

A Minimal Fake Implementation

the fake is a minimal implementation just to support testing, so it can be as simple as possible. e.g: use a single instance variable currentChat to hold the chat object.

How to pass the failing test?

• adding functionality, a tiny slice at a time, until eventually make the test pass. following this approach will makes our progress much more predicable. focusing on just one aspect at a time helps us to make sure we understand it.

• writing a small amount of ugly code and seeing how it falls out. it helps us to test our ideas before we've gone too far, and sometimes the results can be surprising.

The Necessary Minimum

The point is to design and validate the initial structure of the end-to-end system -- where end-to-end includes deployment to a working environment -- to prove that our choices of packages, libraries, and tooling will actually work. A sense of urgency will help the team to strip the functionality down to the absolute minimum sufficient to test their assumptions.

Outside-In Development

• Test-Driven Development is to start with the outside event that triggers the behavior we want to implement and work our way into the code an object at a time, until we reach a visible effect indicating that we've achieved our goal.

• Entry point is the event that triggers the next round of behavior we want to make work.

Defer Decisions

helps us focus on the immediate task without getting dragged into thinking about the next significant chunk of functionality.

Dynamic as well as Static Design

We should consider more than one view when refactoring code. Refactoring is, after all, design activity, which means we need them all the time rather than periodically. Refactoring is so focused on static structure (class & interface) that it's easy to lose sight of an application's dynamic structure (instances and threads). Sometimes we just need to step back and draw out an interaction diagram.