3 files changed, 7 insertions, 5 deletions
diff --git a/test/-ext-/string/test_cstr.rb b/test/-ext-/string/test_cstr.rb
index 2083016db2..d909781700 100644
--- a/test/-ext-/string/test_cstr.rb
+++ b/test/-ext-/string/test_cstr.rb
@@ -13,13 +13,13 @@ class Test_StringCStr < Test::Unit::TestCase
   end
 
   def test_long
-    s = Bug::String.new("abcdef")*100000
+    s = Bug::String.new(Bug::String.new("abcdef")*100000)
     s.cstr_unterm('x')
     assert_equal(0, s.cstr_term, Bug4319)
   end
 
   def test_shared
-    s = Bug::String.new("abcdef")*5
+    s = Bug::String.new(Bug::String.new("abcdef")*5)
     s = s.unterminated_substring(0, 29)
     assert_equal(0, s.cstr_term, Bug4319)
   end
@@ -28,7 +28,7 @@ class Test_StringCStr < Test::Unit::TestCase
     s0 = Bug::String.new("abcdefgh"*8)
 
     [4, 4*3-1, 8*3-1, 64].each do |n|
-      s = s0[0, n]
+      s = Bug::String.new(s0[0, n])
       s.cstr_unterm('x')
       s.freeze
       assert_equal(0, s.cstr_term)
@@ -67,7 +67,7 @@ class Test_StringCStr < Test::Unit::TestCase
     n = 100
     len = str.size * n
     WCHARS.each do |enc|
-      s = Bug::String.new(str.encode(enc))*n
+      s = Bug::String.new(Bug::String.new(str.encode(enc))*n)
       s.cstr_unterm('x')
       assert_nothing_raised(ArgumentError, enc.name) {s.cstr_term}
       s.set_len(s.bytesize / 2)
diff --git a/test/-ext-/string/test_ellipsize.rb b/test/-ext-/string/test_ellipsize.rb
index d7947041d5..d340abd58a 100644
--- a/test/-ext-/string/test_ellipsize.rb
+++ b/test/-ext-/string/test_ellipsize.rb
@@ -10,7 +10,7 @@ class Test_StringEllipsize < Test::Unit::TestCase
   def assert_equal_with_class(expected, result, *rest)
     assert_equal(expected.encoding, result.encoding, *rest)
     assert_equal(expected, result, result.encoding.name)
-    assert_instance_of(Bug::String, result, *rest)
+    assert_instance_of(String, result, *rest)
   end
 
   def test_longer
diff --git a/test/ruby/test_string.rb b/test/ruby/test_string.rb
index 810c700c8c..4814872789 100644
--- a/test/ruby/test_string.rb
+++ b/test/ruby/test_string.rb
@@ -2089,6 +2089,8 @@ CODE
 
   def test_swapcase
     assert_equal(S("hi&LOW"), S("HI&low").swapcase)
+    s = S("")
+    assert_not_same(s, s.swapcase)
   end
 
   def test_swapcase!