Add test for expense_email method in MaintainerMailer

test/mailers/maintainer_mailer_test.rb

@@ -44,4 +44,51 @@ class MaintainerMailerTest < ActionMailer::TestCase
     assert_includes email.html_part.body.to_s, "font-family: system-ui"
     assert_includes email.html_part.body.to_s, "color: #1D1D28"
   end
+
+  test "expense_email" do
+    data = {"draftKey" => "123"}
+    project_allocation = create(:project_allocation)
+    invitation = Invitation.create!(email: "[email protected]", project_allocation: project_allocation, data: data, member_invitation_id: 123)
+    maintainer_email = "[email protected]"
+    package = "example-project"
+    funders = "Sentry"
+    amount = "$500.00"
+    invite_token = "123456"
+    decline_deadline = (Time.now + 14.days).strftime("%B %d, %Y")
+    fund = create(:fund)
+
+    # Send the email
+    email = MaintainerMailer.expense_email(
+      invitation,
+      maintainer_email,
+      package,
+      funders,
+      amount,
+      invite_token,
+      decline_deadline,
+      fund
+    )
+
+    # Assert email properties
+    assert_emails 1 do
+      email.deliver_now
+    end
+
+    assert_equal ["[email protected]"], email.to
+    assert_equal ["[email protected]"], email.from
+    assert_equal "Payment details for your work maintaining #{package}", email.subject
+
+    # Assert email body contains expected content
+    assert_includes email.html_part.body.to_s, "Sentry"
+    assert_includes email.html_part.body.to_s, invite_token
+    assert_includes email.html_part.body.to_s, decline_deadline
+    assert_includes email.html_part.body.to_s, 'src="https://funds.ecosyste.ms'
+
+    assert_includes email.text_part.body.to_s, "Sentry"
+    assert_includes email.text_part.body.to_s, invite_token
+    assert_includes email.text_part.body.to_s, decline_deadline
+
+    assert_includes email.html_part.body.to_s, "font-family: system-ui"
+    assert_includes email.html_part.body.to_s, "color: #1D1D28"
+  end
 end