diff --git a/test/ruby/test_weakmap.rb b/test/ruby/test_weakmap.rb
new file mode 100644
index 0000000000..383b5e1f31
--- /dev/null
+++ b/test/ruby/test_weakmap.rb
@@ -0,0 +1,96 @@
+require 'test/unit'
+require_relative 'envutil'
+
+class TestWeakMap < Test::Unit::TestCase
+  def setup
+    @wm = ObjectSpace::WeakMap.new
+  end
+
+  def test_map
+    x = Object.new
+    k = "foo"
+    @wm[k] = x
+    assert_same(x, @wm[k])
+    assert_not_same(x, @wm["FOO".downcase])
+  end
+
+  def test_include?
+    m = __callee__[/test_(.*)/, 1]
+    x = Object.new
+    k = "foo"
+    @wm[k] = x
+    assert_send([@wm, m, k])
+    assert_not_send([@wm, m, "FOO".downcase])
+    x = nil
+    GC.start
+    assert_not_send([@wm, m, k])
+  end
+  alias test_member? test_include?
+  alias test_key? test_include?
+
+  def test_each
+    m = __callee__[/test_(.*)/, 1]
+    x1 = Object.new
+    k1 = "foo"
+    @wm[k1] = x1
+    x2 = Object.new
+    k2 = "bar"
+    @wm[k2] = x2
+    n = 0
+    @wm.__send__(m) do |k, v|
+      assert_match(/\A(?:foo|bar)\z/, k)
+      case k
+      when /foo/
+        assert_same(k1, k)
+        assert_same(x1, v)
+      when /bar/
+        assert_same(k2, k)
+        assert_same(x2, v)
+      end
+      n += 1
+    end
+    assert_equal(2, n)
+  end
+
+  def test_each_key
+    x1 = Object.new
+    k1 = "foo"
+    @wm[k1] = x1
+    x2 = Object.new
+    k2 = "bar"
+    @wm[k2] = x2
+    n = 0
+    @wm.each_key do |k|
+      assert_match(/\A(?:foo|bar)\z/, k)
+      case k
+      when /foo/
+        assert_same(k1, k)
+      when /bar/
+        assert_same(k2, k)
+      end
+      n += 1
+    end
+    assert_equal(2, n)
+  end
+
+  def test_each_value
+    x1 = "foo"
+    k1 = Object.new
+    @wm[k1] = x1
+    x2 = "bar"
+    k2 = Object.new
+    @wm[k2] = x2
+    n = 0
+    @wm.each_value do |v|
+      assert_match(/\A(?:foo|bar)\z/, v)
+      case v
+      when /foo/
+        assert_same(x1, v)
+      when /bar/
+        assert_same(x2, v)
+      end
+      n += 1
+    end
+    assert_equal(2, n)
+  end
+end