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Testing SMTP MAIL FROM Command Implementation in Postal

This test suite validates the SMTP server client’s MAIL FROM command handling in Postal, focusing on proper email protocol sequence and state management.

Test Coverage Overview

The test suite provides comprehensive coverage of MAIL FROM command behavior in SMTP transactions.

Validates protocol sequence requiring HELO before MAIL FROM
Tests transaction reset functionality
Verifies correct mail from address storage
Covers state transitions during command processing

Implementation Analysis

The testing approach utilizes RSpec’s behavior-driven development patterns to validate SMTP protocol implementation.

Tests employ subject/let declarations for setup, expectation matching for responses, and state verification through instance variables.

Uses RSpec describe blocks for context organization
Implements mock expectations for transaction resets
Validates both successful and error scenarios

Technical Details

Testing Framework: RSpec
Test Environment: Rails helper integration
Module Structure: Nested within SMTPServer namespace
State Management: Tracks client state transitions
Mock Objects: Used for transaction reset verification

Best Practices Demonstrated

The test suite exemplifies clean testing practices with clear separation of concerns and thorough edge case coverage.

Isolated test contexts with proper setup
Clear test descriptions matching functionality
Comprehensive state validation
Proper use of RSpec’s expectation syntax
Efficient test organization within describe blocks

postalserver/postal

spec/lib/smtp_server/client/mail_from_spec.rb

            
# frozen_string_literal: true

require "rails_helper"

module SMTPServer

  describe Client do
    let(:ip_address) { "1.2.3.4" }
    subject(:client) { described_class.new(ip_address) }

    describe "MAIL FROM" do
      it "returns an error if no HELO is provided" do
        expect(client.handle("MAIL FROM: [email protected]")).to eq "503 EHLO/HELO first please"
        expect(client.state).to eq :welcome
      end

      it "resets the transaction when called" do
        expect(client).to receive(:transaction_reset).and_call_original.at_least(3).times
        client.handle("HELO test.example.com")
        client.handle("MAIL FROM: [email protected]")
        client.handle("MAIL FROM: [email protected]")
      end

      it "sets the mail from address" do
        client.handle("HELO test.example.com")
        expect(client.handle("MAIL FROM: [email protected]")).to eq "250 OK"
        expect(client.state).to eq :mail_from_received
        expect(client.instance_variable_get("@mail_from")).to eq "[email protected]"
      end
    end
  end

end