3 files changed, 21 insertions, 5 deletions
diff --git a/actionmailer/test/base_test.rb b/actionmailer/test/base_test.rb
index 977e0e201e..4124aa00bd 100644
--- a/actionmailer/test/base_test.rb
+++ b/actionmailer/test/base_test.rb
@@ -506,8 +506,8 @@ class BaseTest < ActiveSupport::TestCase
   test "should respond to action methods" do
     assert_respond_to BaseMailer, :welcome
     assert_respond_to BaseMailer, :implicit_multipart
-    assert !BaseMailer.respond_to?(:mail)
-    assert !BaseMailer.respond_to?(:headers)
+    assert_not_respond_to BaseMailer, :mail
+    assert_not_respond_to BaseMailer, :headers
   end
 
   test "calling just the action should return the generated mail object" do
@@ -725,6 +725,15 @@ class BaseTest < ActiveSupport::TestCase
     assert(ProcMailer.welcome["x-has-to-proc"].to_s == "symbol")
   end
 
+  test "proc default values can have arity of 1 where arg is a mailer instance" do
+    assert_equal(ProcMailer.welcome["X-Lambda-Arity-1-arg"].to_s, "complex_value")
+    assert_equal(ProcMailer.welcome["X-Lambda-Arity-1-self"].to_s, "complex_value")
+  end
+
+  test "proc default values with fixed arity of 0 can be called" do
+    assert_equal("0", ProcMailer.welcome["X-Lambda-Arity-0"].to_s)
+  end
+
   test "we can call other defined methods on the class as needed" do
     mail = ProcMailer.welcome
     assert_equal("Thanks for signing up this afternoon", mail.subject)
diff --git a/actionmailer/test/caching_test.rb b/actionmailer/test/caching_test.rb
index ae4e7bf57e..574840c30e 100644
--- a/actionmailer/test/caching_test.rb
+++ b/actionmailer/test/caching_test.rb
@@ -105,7 +105,7 @@ class FragmentCachingTest < BaseCachingTest
 
     html_safe = @mailer.read_fragment("name")
     assert_equal content, html_safe
-    assert html_safe.html_safe?
+    assert_predicate html_safe, :html_safe?
   end
 end
 
@@ -262,7 +262,7 @@ class ViewCacheDependencyTest < BaseCachingTest
   end
 
   def test_view_cache_dependencies_are_empty_by_default
-    assert NoDependenciesMailer.new.view_cache_dependencies.empty?
+    assert_empty NoDependenciesMailer.new.view_cache_dependencies
   end
 
   def test_view_cache_dependencies_are_listed_in_declaration_order
diff --git a/actionmailer/test/mailers/proc_mailer.rb b/actionmailer/test/mailers/proc_mailer.rb
index b7cf53eb4a..76e730bb79 100644
--- a/actionmailer/test/mailers/proc_mailer.rb
+++ b/actionmailer/test/mailers/proc_mailer.rb
@@ -4,12 +4,19 @@ class ProcMailer < ActionMailer::Base
   default to: "system@test.lindsaar.net",
           "X-Proc-Method" => Proc.new { Time.now.to_i.to_s },
           subject: Proc.new { give_a_greeting },
-          "x-has-to-proc" => :symbol
+          "x-has-to-proc" => :symbol,
+          "X-Lambda-Arity-0" => ->() { "0" },
+          "X-Lambda-Arity-1-arg" => ->(arg) { arg.computed_value },
+          "X-Lambda-Arity-1-self" => ->(_) { self.computed_value }
 
   def welcome
     mail
   end
 
+  def computed_value
+    "complex_value"
+  end
+
   private
 
     def give_a_greeting