diff --git a/ChangeLog b/ChangeLog
index 112699e24b..e93271b4b8 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,12 @@
+Thu Jun  5 23:56:18 2008  Yusuke Endoh  <mame@tsg.ne.jp>
+
+	* test/ruby/test_gc.rb: add tests to achieve over 90% test coverage of
+	  gc.c.
+
+	* test/ruby/test_objectspace.rb: ditto.
+
+	* test/ruby/test_marshal.rb: ditto.
+
 Thu Jun  5 23:40:08 2008  Yusuke Endoh  <mame@tsg.ne.jp>
 
 	* gc.c (rb_objspace_alloc): this function is needed only when
diff --git a/test/ruby/test_gc.rb b/test/ruby/test_gc.rb
index 72c38e4b27..42b249d0dc 100644
--- a/test/ruby/test_gc.rb
+++ b/test/ruby/test_gc.rb
@@ -32,4 +32,23 @@ class TestGc < Test::Unit::TestCase
 
     GC.stress = prev_stress
   end
+
+  def test_enable_disable
+    GC.enable
+    assert_equal(false, GC.enable)
+    assert_equal(false, GC.disable)
+    assert_equal(true, GC.disable)
+    assert_equal(true, GC.disable)
+    assert_nil(GC.start)
+    assert_equal(true, GC.enable)
+    assert_equal(false, GC.enable)
+  ensure
+    GC.enable
+  end
+
+  def test_count
+    c = GC.count
+    GC.start
+    assert_operator(c, :<, GC.count)
+  end
 end
diff --git a/test/ruby/test_marshal.rb b/test/ruby/test_marshal.rb
index 2c69367e05..c0e6f996e9 100644
--- a/test/ruby/test_marshal.rb
+++ b/test/ruby/test_marshal.rb
@@ -152,4 +152,20 @@ class TestMarshal < Test::Unit::TestCase
     eval("C3 = Struct.new(:foo, :baz)")
     assert_raise(TypeError) { Marshal.load(m) }
   end
+
+  class C4
+    def initialize(gc)
+      @gc = gc
+    end
+    def _dump(s)
+      GC.start if @gc
+      "foo"
+    end
+  end
+
+  def test_gc
+    assert_nothing_raised do
+      Marshal.dump((0..1000).map {|x| C4.new(x % 50 == 25) })
+    end
+  end
 end
diff --git a/test/ruby/test_objectspace.rb b/test/ruby/test_objectspace.rb
index 0b3eea4e09..c82c26a71f 100644
--- a/test/ruby/test_objectspace.rb
+++ b/test/ruby/test_objectspace.rb
@@ -1,4 +1,5 @@
 require 'test/unit'
+require_relative 'envutil'
 
 class TestObjectSpace < Test::Unit::TestCase
   def self.deftest_id2ref(obj)
@@ -53,4 +54,18 @@ End
     assert_same(h0, h)
     assert_equal(0, h0[:T_FOO])
   end
+
+  def test_finalizer
+    EnvUtil.rubyexec("-e", <<-END) do |w, r, e|
+      a = []
+      ObjectSpace.define_finalizer(a) { p :ok }
+      b = a.dup
+      ObjectSpace.define_finalizer(a) { p :ok }
+    END
+      assert_equal("", e.read)
+      assert_equal(":ok\n:ok\n:ok\n:ok\n", r.read)
+
+      assert_raise(ArgumentError) { ObjectSpace.define_finalizer([], Object.new) }
+    end
+  end
 end