test: Shared test infrastructure — MockHttpMessageHandler, fixtures & helpers

[teesofttech]

Overview

Before building per-gateway test files, establish the shared test infrastructure that all unit and integration tests will rely on.

What to Build

MockHttpMessageHandler

A reusable DelegatingHandler (or implementation of HttpMessageHandler) that:

• Accepts a list of (method, url pattern, statusCode, responseBody) tuples to queue up
• Asserts the correct HTTP method and URL was called
• Supports multiple sequential responses for multi-call gateways (e.g. Monnify OAuth + init, Interswitch OAuth + pay)
• Throws InvalidOperationException if an unexpected request is made

TestFixtures

• PaymentRequestFactory.Build() — returns a valid PaymentRequest with sensible test defaults
• RefundRequestFactory.Build() — returns a valid RefundRequest
• GatewayConfigFactory.BuildPaystack(secretKey) — returns a PaymentGatewayConfig with Paystack configured (one per gateway)

IntegrationTestBase

• Abstract base class that checks for required env vars and calls Skip.IfNot() (or Assert.Skip()) when missing
• Reads env vars from .env.test via dotenv or directly from environment
• Logs which env vars are missing so CI output is clear

Test Category Traits

• [Trait("Category", "Unit")] on all unit test classes
• [Trait("Category", "Integration")] on all integration test classes
• Add .runsettings to allow running only unit tests with dotnet test --filter Category=Unit

Directory Structure

PayBridge.SDK.Test/
  Unit/
    PaystackGatewayTests.cs
    FlutterwaveGatewayTests.cs
    ... (one per gateway)
  Integration/
    PaystackIntegrationTests.cs
    ... (one per gateway)
  Helpers/
    MockHttpMessageHandler.cs
    PaymentRequestFactory.cs
    GatewayConfigFactory.cs
    IntegrationTestBase.cs
  PayBridgeTests.cs   (existing smoke tests)

Acceptance Criteria

• MockHttpMessageHandler can intercept and respond to HTTP calls without hitting the network
• All factory helpers produce valid objects accepted by gateway constructors
• IntegrationTestBase correctly skips tests when env vars are not set
• dotnet test --filter Category=Unit runs only unit tests
• dotnet test --filter Category=Integration runs only integration tests