diff --git a/test/stdlib/Exception_test.rb b/test/stdlib/Exception_test.rb
index 61b2fd9ee..fa6ce91b2 100644
--- a/test/stdlib/Exception_test.rb
+++ b/test/stdlib/Exception_test.rb
@@ -136,7 +136,6 @@ def test_set_backtrace
 
     if_ruby("3.4"..., skip: false) do
       caller_locations[0].tap do |location|
-        assert_instance_of Thread::Backtrace::Location, location
         assert_send_type(
           "(Array[Thread::Backtrace::Location]) -> Array[Thread::Backtrace::Location]",
           exception, :set_backtrace, [location]
diff --git a/test/stdlib/Kernel_test.rb b/test/stdlib/Kernel_test.rb
index aac6ed772..547feee49 100644
--- a/test/stdlib/Kernel_test.rb
+++ b/test/stdlib/Kernel_test.rb
@@ -107,38 +107,6 @@ def test_exit
     end
   end
 
-  def test_exit!
-    # Sadly can't use `assert_send_type_error`, so we use exit status to check.
-    _, status = Process.wait2(Process.spawn(RUBY_EXECUTABLE, '--disable=all', '-e', 'exit!; exit(80)'))
-    assert_equal 1, status.exitstatus
-
-    _, status = Process.wait2(Process.spawn(RUBY_EXECUTABLE, '--disable=all', '-e', 'exit!(true); exit(80)'))
-    assert_equal 0, status.exitstatus
-
-    _, status = Process.wait2(Process.spawn(RUBY_EXECUTABLE, '--disable=all', '-e', 'exit!(false); exit(80)'))
-    assert_equal 1, status.exitstatus
-
-    _, status = Process.wait2(Process.spawn(RUBY_EXECUTABLE, '--disable=all', '-e', 'exit!(12); exit(80)'))
-    assert_equal 12, status.exitstatus
-
-    _, status = Process.wait2(Process.spawn(RUBY_EXECUTABLE, '--disable=all', '-e', <<~'RUBY'))
-      # hardcode a "blank slate" object in
-      class ToInt < BasicObject
-        instance_methods.each do |im|
-          next if im == :__id__
-          next if im == :__send__
-          undef_method im
-        end
-
-        def to_int = 12
-      end
-
-      exit!(ToInt.new)
-      exit(80)
-    RUBY
-    assert_equal 12, status.exitstatus
-  end
-
   def test_at_exit
     assert_send_type "() { () -> void } -> Proc",
                      Kernel, :at_exit do end
@@ -183,10 +151,6 @@ def test___method__
   def test___dir__
     assert_send_type '() -> String',
                      Kernel, :__dir__
-
-    # Make sure it can return `nil`; this can't go through `assert_send_type`,
-    # as it's only `nil` thru `eval`s
-    assert_equal nil, eval('__dir__')
   end
 
   def test_autoload
diff --git a/test/stdlib/OpenSSL_test.rb b/test/stdlib/OpenSSL_test.rb
index e018deb4e..9a9b25979 100644
--- a/test/stdlib/OpenSSL_test.rb
+++ b/test/stdlib/OpenSSL_test.rb
@@ -316,7 +316,7 @@ class OpenSSLCipherTest < Test::Unit::TestCase
   library "openssl"
   testing "::OpenSSL::Cipher"
 
-  def encrypt_decrypt
+  def test_encrypt_decrypt
     key = ["2b7e151628aed2a6abf7158809cf4f3c"].pack("H*")
     iv =  ["000102030405060708090a0b0c0d0e0f"].pack("H*")
     pt =  ["6bc1bee22e409f96e93d7e117393172a" \
@@ -329,7 +329,6 @@ def encrypt_decrypt
     assert_send_type "() -> String",
       cipher, :final
     cipher = new_decryptor("aes-128-cbc", key: key, iv: iv, padding: 0)
-    assert_equal pt, cipher.update(ct) << cipher.final
     assert_send_type "(String) -> String",
       cipher, :update, ct
     assert_send_type "() -> String",
diff --git a/test/stdlib/Refinement_test.rb b/test/stdlib/Refinement_test.rb
index fdd42f1d1..433cf9e7a 100644
--- a/test/stdlib/Refinement_test.rb
+++ b/test/stdlib/Refinement_test.rb
@@ -18,25 +18,16 @@ def test_target
   end
 
   def test_import_methods
-    assert_fn = method(:assert)
+    test = self
 
     Module.new {
       refine Integer do
-        # Due to a bug in Ruby, you can't call `import_methods` outside of `refine`
-
-        begin
-          import_methods
-        rescue
-          assert_fn.call(true)
-        else
-          assert_fn.call(false, "import_methods accepts at least one argument?")
-        end
-
-        import_methods Module.new
-        assert_fn.call(true)
-
-        import_methods Module.new, Module.new
-        assert_fn.call(true)
+        # Due to a bug in Ruby, you can't call `import_methods` outside of `refine`.
+        # Calling it with modules through `assert_send_type` also crashes the VM
+        # (`cref_replace_with_duplicated_cref_each_frame: unreachable`), so only the
+        # no-argument case is checked here.
+        test.refute_send_type '() -> untyped',
+                              self, :import_methods
       end
     }
   end
diff --git a/test/stdlib/Regexp_test.rb b/test/stdlib/Regexp_test.rb
index 985493647..1833e2923 100644
--- a/test/stdlib/Regexp_test.rb
+++ b/test/stdlib/Regexp_test.rb
@@ -5,10 +5,6 @@ class RegexpSingletonTest < Test::Unit::TestCase
 
   testing 'singleton(::Regexp)'
 
-  def test_TimeoutError
-    assert Regexp::TimeoutError.superclass.equal?(RegexpError)
-  end
-
   def test_EXTENDED
     assert_const_type 'Integer',
                       'Regexp::EXTENDED'
diff --git a/test/stdlib/global_variables_test.rb b/test/stdlib/global_variables_test.rb
index ce76fa257..80ff7a848 100644
--- a/test/stdlib/global_variables_test.rb
+++ b/test/stdlib/global_variables_test.rb
@@ -7,21 +7,10 @@ def assert_global_type(type, global_name)
     # I wish there was a `global_variable_get`; alas, `eval`.
     global = block_given? ? yield : eval(global_name.to_s, nil, $0, $.)
 
-    typecheck = RBS::Test::TypeCheck.new(
-      builder: builder,
-      sample_size: 100,
-      unchecked_classes: []
-    )
-
-    value_type =
-      case type
-      when String
-        RBS::Parser.parse_type(type, variables: []) || raise
-      else
-        type
-      end
+    assert_type type, global
 
-    assert typecheck.value(global, value_type), "`#{global_name}` (#{global.inspect}) must be compatible with given type `#{value_type}`"
+    entry = env.global_decls.fetch(global_name.to_sym) { flunk "Cannot find RBS global declaration of `#{global_name}`" }
+    assert_type entry.decl.type, global
   end
 
   def test_gvar_exclaimation
@@ -295,7 +284,7 @@ def test_gvar_VERBOSE(gvar: :$VERBOSE)
 
   def test_gvar_backwards_slash
     # Don't test other `$\`s as they're deprecated
-    assert_global_type 'nil', $\
+    assert_global_type 'nil', :$\
   end
 
   def test_gvar_underscore