Add test dependencies to build file

Author: mgreter

Build.PL

@@ -178,6 +178,10 @@ my %config = (
         'Test::More' => 0,
         'File::chdir' => 0,
     },
+    test_requires => {
+        'File::chdir' => 0,
+        'Test::Differences' => 0,
+    },
     requires => {
         'perl' => '5.008',
         'File::Slurp' => 0,

t/99_sass_specs.t

@@ -43,12 +43,22 @@ BEGIN
 
 }
 
+use Test::More;
+
+if (eval { require Test::Differences; 1 })
+{
+	plan(tests => 1 + @tests);
+}
+else
+{
+	plan(skip_all => 'Test::Differences not installed');
+}
+
+use_ok('Test::Differences');
+
 # uncomment to debug a single test case
 # @tests = grep { $_->[0] =~ m/199/ } @tests;
 
-use Test::More tests => scalar @tests;
-use Test::Differences;
-
 use CSS::Sass;
 
 sub read_file