Dynamic Mock Server for Mobile App Testing

2 posts · Sep 2018 – Apr 2019

What this trail covers

Grab has developed Loki, a dynamic mock server for local box testing of mobile apps. Loki simulates backend services over HTTP and TCP protocols, allowing developers to test complex use cases without external dependencies. It supports runtime response generation via JavaScript injection, sequential responses for API endpoints, and configurable message delimiters for TCP. Loki can run in Docker containers locally or in CI, with pluggable storage options (MySQL, in-memory cache, Redis) to manage mock expectations.

All Grab trails

Apr 2019Loki, a Dynamic Mock Server for HTTP/TCP TestingThis post details the technical challenges and solutions for building Loki, a dynamic mock server for mobile app testing. It covers mocking TCP with long-running connections and message delimiters, supporting runtime response generation via JavaScript injection, and defining response sequences for API endpoints. The architecture and usage of Loki for both HTTP and TCP mocking are explained, along with sample use cases.
Sep 2018Mockers - Overcoming Testing Challenges at GrabThis post introduces Mockers, a Go SDK and CLI tool for managing a central monorepo of mock servers at Grab. Mockers simulates a staging environment on developer local boxes, expanding the scope of local box testing to include functional, resiliency, and contract tests. It generates mock servers for HTTP and gRPC microservices based on API specifications (Swagger for HTTP, protobuf for gRPC). Key features include automatic contract verification, out-of-the-box resiliency testing with repeatable tests (integrating with a chaos SDK), and simplified management of mock servers via CLI commands. The post also discusses the limitations of conventional staging environments and differentiates Mockers from unit tests with code mocks.
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