diff --git a/actionpack/test/controller/flash_hash_test.rb b/actionpack/test/controller/flash_hash_test.rb
index 6b3abdd5beb9a0e84d868227082abdb171a9e2f3..45b598a5941bff1ca36efdba7a9c9113cb1c734e 100644
--- a/actionpack/test/controller/flash_hash_test.rb
+++ b/actionpack/test/controller/flash_hash_test.rb
@@ -63,10 +63,10 @@ def test_to_session_value
       assert_equal({ "flashes" => { "foo" => "bar" }, "discard" => [] }, @hash.to_session_value)
 
       @hash.discard("foo")
-      assert_equal(nil, @hash.to_session_value)
+      assert_nil(@hash.to_session_value)
 
       @hash.sweep
-      assert_equal(nil, @hash.to_session_value)
+      assert_nil(@hash.to_session_value)
     end
 
     def test_from_session_value
@@ -75,7 +75,7 @@ def test_from_session_value
       session = Marshal.load(Base64.decode64(rails_3_2_cookie))
       hash = Flash::FlashHash.from_session_value(session["flash"])
       assert_equal({ "greeting" => "Hello" }, hash.to_hash)
-      assert_equal(nil, hash.to_session_value)
+      assert_nil(hash.to_session_value)
     end
 
     def test_from_session_value_on_json_serializer
@@ -84,7 +84,7 @@ def test_from_session_value_on_json_serializer
       hash = Flash::FlashHash.from_session_value(session["flash"])
 
       assert_equal({ "greeting" => "Hello" }, hash.to_hash)
-      assert_equal(nil, hash.to_session_value)
+      assert_nil(hash.to_session_value)
       assert_equal "Hello", hash[:greeting]
       assert_equal "Hello", hash["greeting"]
     end
diff --git a/activerecord/test/cases/adapters/mysql2/json_test.rb b/activerecord/test/cases/adapters/mysql2/json_test.rb
index 5d4db1be91953b5eba9d343031edd5f7e86af6cf..6954006003961bad18351a903f0a1f68567efcdd 100644
--- a/activerecord/test/cases/adapters/mysql2/json_test.rb
+++ b/activerecord/test/cases/adapters/mysql2/json_test.rb
@@ -93,7 +93,7 @@ def test_select_multikey
     def test_null_json
       @connection.execute "insert into json_data_type (payload) VALUES(null)"
       x = JsonDataType.first
-      assert_equal(nil, x.payload)
+      assert_nil(x.payload)
     end
 
     def test_select_array_json_value
@@ -111,7 +111,7 @@ def test_select_nil_json_after_create
     def test_select_nil_json_after_update
       json = JsonDataType.create(payload: "foo")
       x = JsonDataType.where(payload: nil).first
-      assert_equal(nil, x)
+      assert_nil(x)
 
       json.update_attributes payload: nil
       x = JsonDataType.where(payload: nil).first
diff --git a/activerecord/test/cases/adapters/postgresql/bytea_test.rb b/activerecord/test/cases/adapters/postgresql/bytea_test.rb
index dc0df8715ad746fff953822f89163baca5bc882d..5c207116c4fcf7e2af54ece517df4e1e7c111d51 100644
--- a/activerecord/test/cases/adapters/postgresql/bytea_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/bytea_test.rb
@@ -52,7 +52,7 @@ def test_type_cast_binary_value
   end
 
   def test_type_case_nil
-    assert_equal(nil, @type.deserialize(nil))
+    assert_nil(@type.deserialize(nil))
   end
 
   def test_read_value
@@ -66,7 +66,7 @@ def test_read_value
   def test_read_nil_value
     @connection.execute "insert into bytea_data_type (payload) VALUES (null)"
     record = ByteaDataType.first
-    assert_equal(nil, record.payload)
+    assert_nil(record.payload)
     record.delete
   end
 
@@ -106,8 +106,8 @@ def test_write_binary
   def test_write_nil
     record = ByteaDataType.create(payload: nil)
     assert_not record.new_record?
-    assert_equal(nil, record.payload)
-    assert_equal(nil, ByteaDataType.where(id: record.id).first.payload)
+    assert_nil(record.payload)
+    assert_nil(ByteaDataType.where(id: record.id).first.payload)
   end
 
   class Serializer
diff --git a/activerecord/test/cases/adapters/postgresql/json_test.rb b/activerecord/test/cases/adapters/postgresql/json_test.rb
index 991dedfdf119ec87d82fe8023b6e00fa7968bceb..93558ac4d294f9e87fac82f47098fa701dac5b3e 100644
--- a/activerecord/test/cases/adapters/postgresql/json_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/json_test.rb
@@ -110,7 +110,7 @@ def test_select_multikey
   def test_null_json
     @connection.execute "insert into json_data_type (payload) VALUES(null)"
     x = JsonDataType.first
-    assert_equal(nil, x.payload)
+    assert_nil(x.payload)
   end
 
   def test_select_nil_json_after_create
@@ -122,7 +122,7 @@ def test_select_nil_json_after_create
   def test_select_nil_json_after_update
     json = JsonDataType.create(payload: "foo")
     x = JsonDataType.where(payload: nil).first
-    assert_equal(nil, x)
+    assert_nil(x)
 
     json.update_attributes payload: nil
     x = JsonDataType.where(payload: nil).first
diff --git a/activerecord/test/cases/adapters/postgresql/uuid_test.rb b/activerecord/test/cases/adapters/postgresql/uuid_test.rb
index c6b84482d60e96d22d25ad11f7f70e3a38111552..f34d50e25cc7adfb03037c772c77c75799a34dcd 100644
--- a/activerecord/test/cases/adapters/postgresql/uuid_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/uuid_test.rb
@@ -71,12 +71,12 @@ def test_data_type_of_uuid_types
 
   def test_treat_blank_uuid_as_nil
     UUIDType.create! guid: ""
-    assert_equal(nil, UUIDType.last.guid)
+    assert_nil(UUIDType.last.guid)
   end
 
   def test_treat_invalid_uuid_as_nil
     uuid = UUIDType.create! guid: "foobar"
-    assert_equal(nil, uuid.guid)
+    assert_nil(uuid.guid)
   end
 
   def test_invalid_uuid_dont_modify_before_type_cast
diff --git a/activesupport/test/core_ext/hash_ext_test.rb b/activesupport/test/core_ext/hash_ext_test.rb
index ff12632f84bdc129d58c088432d6109d4f2a3822..698a67b0b37c360df7676a49c92cf55043f32714 100644
--- a/activesupport/test/core_ext/hash_ext_test.rb
+++ b/activesupport/test/core_ext/hash_ext_test.rb
@@ -1017,7 +1017,7 @@ def test_compact!
     assert_equal({}, h)
 
     h = @symbols.dup
-    assert_equal(nil, h.compact!)
+    assert_nil(h.compact!)
     assert_equal(@symbols, h)
   end