BSD host properly tests for `nfsd` binary

lib/vagrant/hosts/bsd.rb

@@ -5,8 +5,8 @@ module Vagrant
       include Util
 
       def nfs?
-        # TODO: verify it exists
+        system("which nfsd")
-        true
+        $?.to_i == 0
       end
 
       def nfs_export(ip, folders)

test/vagrant/hosts/bsd_test.rb

@@ -10,8 +10,22 @@ class BSDHostTest < Test::Unit::TestCase
 
   context "supporting nfs check" do
     should "support NFS" do
+      @instance.expects(:system).with() do |cmd|
+        `which which`
+        true
+      end
+
       assert @instance.nfs?
     end
+
+    should "not support NFS if nfsd is not found" do
+      @instance.expects(:system).with() do |cmd|
+        `which thisshouldnoteverneverexist`
+        true
+      end
+
+      assert !@instance.nfs?
+    end
   end
 
   context "nfs export" do