devise fixes?

lib/mailers/previews/devise_mailer_preview.rb

@@ -35,9 +35,25 @@ def invitation_instructions_as_volunteer
     preview(volunteer)
   end
 
-  private
+  def email_changed
+    user = params.has_key?(:id) ? User.find_by(id: params[:id]) : User.last
+    if user.nil?
+      DebugPreviewMailer.invalid_user("user")
+    else
+      Devise::Mailer.email_changed(user)
+    end
+  end
 
-  # Unused email types
+  def password_change
+    user = params.has_key?(:id) ? User.find_by(id: params[:id]) : User.last
+    if user.nil?
+      DebugPreviewMailer.invalid_user("user")
+    else
+      Devise::Mailer.password_change(user)
+    end
+  end
+
+  private
 
   def update_invitation_sent_at(model)
     # Set :invitation_sent_at to guarantee the preview works
@@ -47,15 +63,5 @@ def update_invitation_sent_at(model)
   def preview(model)
     Devise::Mailer.invitation_instructions(model, "faketoken")
   end
-
-  def email_changed
-    user = params.has_key?(:id) ? User.find_by(id: params[:id]) : User.last
-    Devise::Mailer.email_changed(user)
-  end
-
-  def password_change
-    user = params.has_key?(:id) ? User.find_by(id: params[:id]) : User.last
-    Devise::Mailer.password_change(user)
-  end
 end
 # :nocov:

spec/mailers/previews/devise_mailer_preview_spec.rb

@@ -55,4 +55,50 @@
 
     it { expect(message.to).to eq [volunteer.email] }
   end
+
+  describe "#email_changed" do
+    context "When no ID is passed" do
+      let(:preview) { described_class.new }
+      let(:email) { preview.email_changed }
+
+      it { expect(email.to).to eq [user.email] }
+    end
+
+    context "When passed ID is valid" do
+      let(:preview) { described_class.new(id: user.id) }
+      let(:email) { preview.email_changed }
+
+      it { expect(email.to).to eq [user.email] }
+    end
+
+    context "When passed ID is invalid" do
+      let(:preview) { described_class.new(id: -1) }
+      let(:email) { preview.email_changed }
+
+      it { expect(email.to).to eq ["missing_user@example.com"] }
+    end
+  end
+
+  describe "#password_change" do
+    context "When no ID is passed" do
+      let(:preview) { described_class.new }
+      let(:email) { preview.password_change }
+
+      it { expect(email.to).to eq [user.email] }
+    end
+
+    context "When passed ID is valid" do
+      let(:preview) { described_class.new(id: user.id) }
+      let(:email) { preview.password_change }
+
+      it { expect(email.to).to eq [user.email] }
+    end
+
+    context "When passed ID is invalid" do
+      let(:preview) { described_class.new(id: -1) }
+      let(:email) { preview.password_change }
+
+      it { expect(email.to).to eq ["missing_user@example.com"] }
+    end
+  end
 end