Added DSL specs and improved error message.

DSL now have basics specs that confirm it works
I splitted file not found and invalid Guardfile
error message because it was confusing to know
in which case you are when it occurs :)

lib/guard/dsl.rb

@@ -3,12 +3,19 @@ module Guard
     
     def self.evaluate_guardfile
       guardfile = "#{Dir.pwd}/Guardfile"
+      if File.exists? guardfile
+        begin
           dsl = new
           dsl.instance_eval(File.read(guardfile.to_s), guardfile.to_s, 1)
         rescue
-      UI.error "Guardfile not found or invalid"
+          UI.error "Invalid Guardfile, original error is:\n#{$!}"
           exit 1
         end
+      else
+        UI.error "No Guardfile in current folder, please create one."
+        exit 1
+      end
+    end
     
     def self.guardfile_included?(guard_name)
       File.read('Guardfile').include?("guard '#{guard_name}'")

spec/fixtures/dsl/invalid_guardfile/Guardfile

@@ -0,0 +1 @@
+Balasfllsd fsdadsg hsla kjsdh jakh kajlsh klsajhgs dklhj

spec/fixtures/dsl/options/Guardfile

@@ -0,0 +1 @@
+guard 'test', :opt_a => 1, :opt_b => 'test'

spec/fixtures/dsl/simple/Guardfile

@@ -0,0 +1 @@
+guard 'test'

spec/fixtures/dsl/watchers/Guardfile

@@ -0,0 +1,4 @@
+guard 'test' do
+  watch('a') { 'b' }
+  watch('c')
+end

spec/guard/dsl_spec.rb

@@ -0,0 +1,55 @@
+require 'spec_helper'
+require 'guard/dsl'
+
+describe Guard::Dsl do
+  subject {Guard::Dsl}
+  
+  it "load a guard from the DSL" do
+    fixture :simple
+    
+    ::Guard.stub!(:add_guard)
+    ::Guard.should_receive(:add_guard).with('test', [], {})
+    subject.evaluate_guardfile
+  end
+  
+  it "write an error message when no Guardfile is found" do
+    fixture :no_guardfile
+    
+    Guard::UI.stub!(:error)
+    Guard::UI.should_receive(:error).with("No Guardfile in current folder, please create one.")
+    lambda { subject.evaluate_guardfile }.should raise_error
+  end
+  
+  it "write an error message when Guardfile is not valid" do
+    fixture :invalid_guardfile
+
+    Guard::UI.stub!(:error)
+    Guard::UI.should_receive(:error).with(/Invalid Guardfile, original error is:\n/)
+    lambda { subject.evaluate_guardfile }.should raise_error
+  end
+  
+  it "receive watchers when specified" do
+    fixture :watchers
+    
+    ::Guard.stub!(:add_guard)
+    ::Guard.should_receive(:add_guard).with('test', anything(), {}) do |name, watchers, options|
+      watchers.size.should eql 2
+    end
+    subject.evaluate_guardfile
+  end
+  
+  it "receive options when specified" do
+    fixture :options
+    
+    ::Guard.stub!(:add_guard)
+    ::Guard.should_receive(:add_guard).with('test', anything(), hash_including(:opt_a, :opt_b))
+    subject.evaluate_guardfile
+  end
+  
+private
+  def fixture name
+    ## Hack to make guard look into the correct fixture folder
+    Dir.stub!(:pwd).and_return("#{@fixture_path}/dsl/#{name}")
+    Dir.pwd.should == "#{@fixture_path}/dsl/#{name}"
+  end
+end