metaprogramming. The accompany-
ing table shows critical topics from the
SWEBOK (software engineering body
of knowledge), 5 the Agile technique for
that topic, and the Rails tool that imple-
ments that technique. Because these
tools are lightweight, seamlessly inte-
grated with Rails, and require virtually
no installation or configuration—some
are delivered as SaaS—students quickly
begin learning important techniques
directly by doing them. We agree with
Confucius: “I hear and I forget. I see and
I remember. I do and I understand.”
Students see and use tools that we can
explain and check, rather than just hear

figure 1. An example feature for a cash register application and one “happy path” user story for that feature.

Feature: Division
In order to avoid silly mistakes
Cashiers must be able to calculate a fraction
Scenario: Regular numbers
Given I have entered 3 into the calculator
And I have entered 2 into the calculator
When I press divide
Then the result should be 1. 5 on the screen

figure 2. the key section of the Cucumber and Ruby code that automates the acceptance test for the user story in figure 1 by matching regular expressions.

Given /I have entered (\d+) into the calculator/ do |n|
@calc.push n.to_i
end
When /I press (\w+)/ do |op|
@result = calc.send op
end
Then /the result should be (.*) on the screen/ do |result|
result.should == result.to_f
end

figure 3. one Agile iteration in our course.

Talk to Customer
Legacy
Design patterns
Behavior-Driven Design (user stories)

Test-Driven Development (unit test)

Measure velocity

lectures about a methodology and then forget to use them in their projects.

For example, the Cucumber tool automates turning customer-under-standable user stories into acceptance tests. Figure 1 is an example feature for a cash register application and one “happy path” user story (called a scenario in Cucumber) for that feature (see http://en.wikipedia.org/ Such tools not only make it easy for students to do what they hear in lecture, but also simplify grading of student effort from a time-intensive subjective evaluation by reading code to a low-effort objective evaluation by measuring it. SimpleCov measures test coverage, saikuro measures cyc-lomatic complexity of the code, flog measures code assignment-branch-condition complexity, reek comments on code quality by highlighting “code smells,”f Cucumber shows the number of user stories completed, and Pivotal Tracker records weekly progress and can point out problems in balance of effort by members of teams. Indeed, these tools make it plausible for the online course to have automatically gradable assignments with some teeth in them.

Compared to Java and its frameworks, Rails programmers have found factors of three to five reductions in number of lines of code, which is one indication of productivity. 6, 8 Rails also helps with a criticism of Agile in that TDD and rapid iteration can lead to poor software architecture. We do teach design patterns (see Figure 3). Indeed, the Rails framework follows the Model View Controller (MVC)g design pattern

f Code smells highlight to sections of code that may be hard to read, maintain, or evolve.

g MVC is a design pattern that separates input logic, business logic, and user interface logic yet provides a loose coupling between them.