diff --git a/lib/action_mailroom/test_helper.rb b/lib/action_mailroom/test_helper.rb
index 06a38f75b6..7f56831f36 100644
--- a/lib/action_mailroom/test_helper.rb
+++ b/lib/action_mailroom/test_helper.rb
@@ -2,11 +2,17 @@ module ActionMailroom
   module TestHelper
     # Create an InboundEmail record using an eml fixture in the format of message/rfc822
     # referenced with +fixture_name+ located in +test/fixtures/files/fixture_name+.
-    def create_inbound_email(fixture_name, status: :processing)
-      raw_email = ActiveStorage::Blob.create_after_upload! \
-            io: file_fixture(fixture_name).open, filename: fixture_name, content_type: 'message/rfc822'
-
-      ActionMailroom::InboundEmail.create!(status: status, raw_email: raw_email)
+    def create_inbound_email_from_fixture(fixture_name, status: :processing)
+      create_inbound_email file_fixture(fixture_name).open, filename: fixture_name, status: status
     end    
+
+    def create_inbound_email_from_mail(status: :processing, &block)
+      create_inbound_email(StringIO.new(Mail.new { instance_eval(&block) }.to_s), status: status)
+    end
+
+    def create_inbound_email(io, filename: 'mail.eml', status: status)
+      ActionMailroom::InboundEmail.create! status: status, raw_email:
+        ActiveStorage::Blob.create_after_upload!(io: io, filename: filename, content_type: 'message/rfc822')
+    end
   end
 end
diff --git a/test/unit/inbound_email/incineration_test.rb b/test/unit/inbound_email/incineration_test.rb
index f2464b8cb8..3de0af3225 100644
--- a/test/unit/inbound_email/incineration_test.rb
+++ b/test/unit/inbound_email/incineration_test.rb
@@ -5,7 +5,7 @@ class ActionMailroom::InboundEmail::IncinerationTest < ActiveSupport::TestCase
     freeze_time
 
     assert_enqueued_with job: ActionMailroom::InboundEmail::IncinerationJob, at: 30.days.from_now do
-      create_inbound_email("welcome.eml").delivered!
+      create_inbound_email_from_fixture("welcome.eml").delivered!
     end
   end
 end
diff --git a/test/unit/mailbox/callbacks_test.rb b/test/unit/mailbox/callbacks_test.rb
index ada6410876..4cafeb3534 100644
--- a/test/unit/mailbox/callbacks_test.rb
+++ b/test/unit/mailbox/callbacks_test.rb
@@ -13,7 +13,7 @@ end
 class ActionMailroom::Mailbox::CallbacksTest < ActiveSupport::TestCase
   setup do
     $before_processing = $after_processing = $around_processing = $processed = false
-    @inbound_email = create_inbound_email("welcome.eml")
+    @inbound_email = create_inbound_email_from_fixture("welcome.eml")
   end
 
   test "all callback types" do
diff --git a/test/unit/mailbox/routing_test.rb b/test/unit/mailbox/routing_test.rb
index 6026686bea..4a8ed10eb0 100644
--- a/test/unit/mailbox/routing_test.rb
+++ b/test/unit/mailbox/routing_test.rb
@@ -13,7 +13,7 @@ end
 class ActionMailroom::Mailbox::RoutingTest < ActiveSupport::TestCase
   setup do
     $processed = false
-    @inbound_email = create_inbound_email("welcome.eml")
+    @inbound_email = create_inbound_email_from_fixture("welcome.eml")
   end
 
   test "string routing" do
@@ -23,7 +23,7 @@ class ActionMailroom::Mailbox::RoutingTest < ActiveSupport::TestCase
 
   test "delayed routing" do
     perform_enqueued_jobs only: ActionMailroom::RoutingJob do
-      another_inbound_email = create_inbound_email("welcome.eml", status: :pending)
+      another_inbound_email = create_inbound_email_from_fixture("welcome.eml", status: :pending)
       assert_equal "Discussion: Let's debate these attachments", $processed
     end
   end
diff --git a/test/unit/mailbox/state_test.rb b/test/unit/mailbox/state_test.rb
index 41fbafbd67..d73ecaa1e2 100644
--- a/test/unit/mailbox/state_test.rb
+++ b/test/unit/mailbox/state_test.rb
@@ -17,7 +17,7 @@ end
 class ActionMailroom::Mailbox::StateTest < ActiveSupport::TestCase
   setup do
     $processed = false
-    @inbound_email = create_inbound_email("welcome.eml")
+    @inbound_email = create_inbound_email_from_fixture("welcome.eml")
   end
 
   test "successful mailbox processing leaves inbound email in delivered state" do
diff --git a/test/unit/router_test.rb b/test/unit/router_test.rb
index 6bfd880b67..fa7ac2ba19 100644
--- a/test/unit/router_test.rb
+++ b/test/unit/router_test.rb
@@ -15,8 +15,12 @@ module ActionMailroom
     end
 
     test "routed to mailbox" do
-      @router.route create_inbound_email("welcome.eml")
-      assert_equal "Discussion: Let's debate these attachments", $processed
+      @router.route create_inbound_email_from_mail {
+        to "replies@example.com"
+        subject "This is a reply"
+      }
+
+      assert_equal "This is a reply", $processed
     end
   end
 end