in_tail: test: Add testcase for path w/ Linux capability

Signed-off-by: Hiroshi Hatake <hatake@clear-code.com>

test/plugin/test_in_tail.rb

@@ -1115,6 +1115,49 @@ def count_timer_object
     end
   end
 
+  sub_test_case "path w/ Linux capability" do
+    def capability_enabled?
+      if Fluent.linux?
+        begin
+          require 'capng'
+          true
+        rescue LoadError
+          false
+        end
+      else
+        false
+      end
+    end
+
+    setup do
+      omit "This environment is not enabled Linux capability handling feature" unless capability_enabled?
+
+      @capng = CapNG.new(:current_process)
+      flexstub(Fluent::Capability) do |klass|
+        klass.should_receive(:new).with(:current_process).and_return(@capng)
+      end
+    end
+
+    data("dac_read_search" => [:dac_read_search, true,  1],
+         "dac_override"    => [:dac_override,    true,  1],
+         "chown"           => [:chown,           false, 0],
+        )
+    test "with partially elevated privileges" do |data|
+      cap, result, readable_paths = data
+      @capng.update(:add, :effective, cap)
+
+      d = create_driver(
+        config_element("ROOT", "", {
+                            "path" => "/var/log/ker*.log", # Use /var/log/kern.log
+                            "tag" => "t1",
+                            "rotate_wait" => "2s"
+                       }) + PARSE_SINGLE_LINE_CONFIG, false)
+
+      assert_equal readable_paths, d.instance.expand_paths.length
+      assert_equal result, d.instance.have_read_capability?
+    end
+  end
+
   def test_pos_file_dir_creation
     config = config_element("", "", {
       "tag" => "tail",