1 files changed, 10 insertions, 0 deletions
diff --git a/actionmailer/test/base_test.rb b/actionmailer/test/base_test.rb
index 531bf58ea9..c07fca5b5e 100644
--- a/actionmailer/test/base_test.rb
+++ b/actionmailer/test/base_test.rb
@@ -307,6 +307,16 @@ class BaseTest < ActiveSupport::TestCase
     assert_equal("HTML Implicit Multipart", email.parts[1].body.encoded)
   end
 
+  test "implicit multipart formats" do
+    email = BaseMailer.implicit_multipart_formats
+    assert_equal(2, email.parts.size)
+    assert_equal("multipart/alternative", email.mime_type)
+    assert_equal("text/plain", email.parts[0].mime_type)
+    assert_equal("Implicit Multipart [:text]", email.parts[0].body.encoded)
+    assert_equal("text/html", email.parts[1].mime_type)
+    assert_equal("Implicit Multipart [:html]", email.parts[1].body.encoded)
+  end
+
   test "implicit multipart with sort order" do
     order = ["text/html", "text/plain"]
     with_default BaseMailer, parts_order: order do