"Use assert_nil if expecting nil from ...:in `...'. This will fail in minitest 6."

actionpack/test/controller/http_token_authentication_test.rb

@@ -166,8 +166,7 @@ class HttpTokenAuthenticationTest < ActionController::TestCase
 
   test "token_and_options returns nil with no value after the equal sign" do
     actual = ActionController::HttpAuthentication::Token.token_and_options(malformed_request).first
-    expected = nil
-    assert_equal(expected, actual)
+    assert_nil actual
   end
 
   test "raw_params returns a tuple of two key value pair strings" do

activesupport/test/core_ext/hash_ext_test.rb

@@ -537,10 +537,10 @@ class HashExtTest < ActiveSupport::TestCase
     get_hash = proc { { a: "foo" }.with_indifferent_access }
     hash = get_hash.call
     assert_equal "foo", hash.delete(:a)
-    assert_equal nil, hash.delete(:a)
+    assert_nil hash.delete(:a)
     hash = get_hash.call
     assert_equal "foo", hash.delete("a")
-    assert_equal nil, hash.delete("a")
+    assert_nil hash.delete("a")
   end
 
   def test_indifferent_select

activesupport/test/safe_buffer_test.rb

@@ -175,6 +175,6 @@ class SafeBufferTest < ActiveSupport::TestCase
 
   test "Should not affect frozen objects when accessing characters" do
     x = "Hello".html_safe
-    assert_equal nil, x[/a/, 1]
+    assert_nil x[/a/, 1]
   end
 end