Matt Fletcher
Atomic Object
latest version at
http://fletcherm.github.com/glsec_2011
Context
Big government agency wants some training
TDD and unit testing
Tools
The usual process
Simple GUI calculator example
Red
void test_ApplicationPresenter_
AllowsNumbersToBeEnteredForTheDivisor() {
ApplicationView_GetDivisor_ExpectAndReturn("21");
ApplicationModel_CheckArgumentFormat
_ExpectAndReturn("21", "3", TRUE);
ApplicationPresenter_DivisorChangedCallback("3");
}void test_ApplicationPresenter_
DoesNotAllowNonNumbersToBeEnteredForTheDivisor() {
ApplicationView_GetDivisor_ExpectAndReturn("21");
ApplicationModel_CheckArgumentFormat
_ExpectAndReturn("21", "j", FALSE);
ApplicationView_UndoDivisorTextChange_Expect();
ApplicationPresenter_DivisorChangedCallback("j");
}Green
void ApplicationPresenter_
DivisorChangedCallback(char* new_text) {
if (ApplicationModel_CheckArgumentFormat(
ApplicationView_GetDivisor(), new_text) == FALSE) {
ApplicationView_UndoDivisorTextChange();
}
}Refactor
- nothing needed here because it's already awesome!
upside
it's tested
good day, bad day, corner cases covered
we know each component works...in isolation
we need to know if these components cooperate
Let's take TDD even further
Sample project
- client - server apps
- put and get (pid, name) tuples for an id
TDD at the system level with Cucumber
Bring in Ruby and Cucumber to help
slightly modified workflow
Feature: client can ping the server
Red system test
Write a test in Gherkin
Feature: Ping command
As a server
I want to respond to clients
wondering if I'm online
Scenario: Responding to a ping
Given the server is online
When I ping the server
Then the client should receive
a positive response
Back it up with Ruby
When /^I ping the server$/ do
TCPSocket.open(IP, PORT) do |conn|
conn.puts "ping"
@response = conn.gets
end
end
Then /^the client should receive
a positive response$/ do
@response.strip.should == "ACK"
end
Red unit tests
Green unit tests
Develop units until you think you're done
Green system tests
Refactor
Red system test
continue developing features
Workflow
- Red system test
- Red unit tests
- Green unit tests
- Refactor units
- Green system test
Feature: Put and get commands
As a server
...
Scenario: Putting and getting multiple pairs
Given the server is online
When I put the pid "1" with the name "init" for id "abc"
And I put the pid "99" with the name "ps" for id "abc"
And I put the pid "187" with the name "ruby" for id "abc"
When I get the pairs for id "abc"
Then the pid "1" with the name "init" should be returned
And the pid "99" with the name "ps" should be returned
And the pid "187" with the name "ruby" should be returned
So what?
Just because you're developing C doesn't mean you can't back it up with something else
Cucumbers don't care how the executables were developed
When /^I run the client with
parameters "([^"]*)"$/ do |params|
When %+I run client.exe #{params}+
end
client.exe could be anything
students in course developed executables in C
cheater executables - written in Ruby, but pass system tests
System tests don't care
Requirement: your system needs clear inputs and outputs
- data over a network (TCP, CAN)
- command-line parameters and output
- digital IO ports
Back to the course
Totals
- 7 cucumber tests for client
- 9 cucumber tests for server
Successes
- All groups got client working
- One - two groups got server working
- Github repository made pushing fixes and changes easy
- Git branches for server, client helped overcome limitations and keep things separated
- Smart group that enjoyed the course and working together
- Gave good feedback on how to improve course and material
- Very involved and interested in Agile PM discussion
- Hinted another group is interested in training as well