Add test coverage for jordansissel#607 (safesystem w/ no $SHELL)

Also: Add missing SecureRandom.uuid under 1.8.x (for the tests)

spec/fpm/package/dir_spec.rb

@@ -3,6 +3,18 @@
 require "fpm/package/dir" # local
 require "stud/temporary"
 
+if RUBY_VERSION =~ /^1\.8/
+  # The following method copied from ruby 1.9.3
+  module SecureRandom
+    def self.uuid
+      ary = self.random_bytes(16).unpack("NnnnnN")
+      ary[2] = (ary[2] & 0x0fff) | 0x4000
+      ary[3] = (ary[3] & 0x3fff) | 0x8000
+      "%08x-%04x-%04x-%04x-%04x%08x" % ary
+    end
+  end
+end
+
 describe FPM::Package::Dir do
   let(:tmpdir) { Stud::Temporary.directory("tmpdir") }
   let(:output) { Stud::Temporary.directory("output") }

spec/fpm/util_spec.rb

@@ -0,0 +1,54 @@
+require "spec_setup"
+require "fpm" # local
+
+describe FPM::Util do
+  subject do
+    Class.new do
+      include FPM::Util
+      def initialize
+        @logger = Cabin::Channel.new
+      end
+    end.new
+  end
+
+  describe "#safe_system" do
+    context "with a missing $SHELL" do
+      before do
+        @orig_shell = ENV["SHELL"]
+        ENV.delete("SHELL")
+      end
+
+      after do
+        ENV["SHELL"] = @orig_shell unless @orig_shell.nil?
+      end
+
+      it "should assume /bin/sh"  do
+        insist { subject.default_shell } == "/bin/sh"
+      end
+
+      it "should still run commands correctly" do
+        # This will raise an exception if we can't run it at all.
+        subject.safesystem("true")
+      end
+    end
+    context "with $SHELL set to an empty string" do 
+      before do
+        @orig_shell = ENV["SHELL"]
+        ENV["SHELL"] = ""
+      end
+
+      after do
+        ENV["SHELL"] = @orig_shell unless @orig_shell.nil?
+      end
+
+      it "should assume /bin/sh"  do
+        insist { subject.default_shell } == "/bin/sh"
+      end
+
+      it "should still run commands correctly" do
+        # This will raise an exception if we can't run it at all.
+        subject.safesystem("true")
+      end
+    end
+  end
+end