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Gospecify: Basic setup of the project's structure

During the last two days I played a bit with GoSpecify by Samuel Tesla, a BDD framework for the Go Language. I'm coming from 4 years of intense Ruby development and, you know, I could not live without a good BDD framework. After watching Samuel Google TechTalk I decided to explore BDD under Go. The first problem I faced and solved was with basic files and folders setup. In this post I'll describe how I managed the issue using project structure and makefiles taken from gospecify project itself.

First of all, let's create the project folder

mkdir fib

Yeah, you guessed right, we'll deal with yet another Fibonacci sequence implementation ;)

Now, move in fib folder and create a basic project structure

cd fib
mkdir src
mkdir spec

As you guess src will contain source files and spec will contain the specs. Now let's go creating a Makefile in the project base path. Create an empty Makefile using your favourite text editor and copy/paste the code below:

all: test
    cd src; make clean
    cd src; gofmt -w *.go
    cd spec; gofmt -w *.go

test: package
      cd spec; $(SPECIFY) *.go
    cd src; make package

These are the up-level's rules with which we will interact. Names are self-explanatory however I'll describe the corresponding actions below:

make clean
    Clean up project folder removing intermediate and backup files
make test
    Run the specs
make format
    Format the source files using gofmt
make package
    Build the package

As you can see, some of the rules above assume there is another Makefile inside src/ folder. Thus, move on src/ and create the following Makefile:

include $(GOROOT)/src/Make.$(GOARCH)
export GC
export LD
export O
SRC=$(wildcard *.go)
all: test
    rm -rf *.[a68] $(TESTPROG) _test *~
test: testpackage
package: $(PACKAGE).a

          gopack grc $@ $(PACKAGE).$O
           $(GC) -o $@ $(SRC)

Note that we have to set the PACKAGE variable with the name of the package (fib in this case). Also, note that the testpackage rule in the Makefile above will create a package named test$(PACKAGE).a. So, in our case, we will get src/testfib.a. We will import this package in our test code to actually run the specs.

At this point, the basic project structure and makefiles are done. Now, we can populate src/ folder with an empty source file (with just the basic package clause within):

cd src
echo "package fib" > fib.go

Now, following BDD convention (test-first approach), let's write our test. Enter in spec/ folder and create spec/fib_spec.go with the code below:

package main
import . "specify"
import t "../src/fib"
func init() {
        Describe("Fib", func() {
                It("should return Fibonacci's next number", func(e Example) {
                        fib := new(t.Fib)
                        fib.N0, fib.N1 = 0, 1

The spec above tell us how we expect the system behaves before actually implement it. In particular, we setup two seed values N0 and N1 and then we query fib about the next value in the sequence using fib.Next() method. For the first five calls we expect the sequence: 1, 1, 2, 3, 5.

If we try to run the specs at this point we get an error of course (we haven't an implementation yet):

$ make
fib_spec.go:9: undefined: testfib.Fib

Open the text editor and paste in src/fib.go the code below:

package fib

type Fib struct {
        N0, N1 int
func (state *Fib) Next() int {
        state.N0, state.N1 = state.N0 + state.N1, state.N0
        return state.N0

If you're new to Go, take your time reading the code. Also consider that I'm still learning this language from the ground up so this could not be the best idiomatic implementation (waiting for suggestions in this case). BTW, for the purpose of this post, our code behave as we expect. In fact, running the specs

$ make test
Passing: 1  Failing: 0  Pending: 0  Errors: 0

they all pass.

Well, that's all for now! You can browse the source files used in this post on github.

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