MockServer vs WireMock

MockServer is a free, self-hosted tool for mocking and proxying HTTP, HTTPS, and gRPC services during isolated testing. It can verify requests as well as stand in for services. Teams can generate mocks and validate traffic against OpenAPI or Swagger contracts, or import recorded sessions from browser HAR files and Postman collections. Beyond HTTP services, it can mock gRPC, AsyncAPI brokers such as Kafka, MQTT, and AMQP, and OAuth2/OIDC providers. Its protocol coverage includes HTTP/1.1, HTTP/2, HTTPS, SOCKS, and experimental HTTP/3, which uses a separate UDP port. For fault-oriented testing, it can add latency, errors, dropped connections, and malformed responses to mocked or proxied traffic. Deployment options include Docker, an executable JAR, Helm/Kubernetes, Testcontainers, Homebrew, and a JVM-less bundle. A web dashboard displays logs, expectations, and recorded traffic; Prometheus metrics and OpenTelemetry tracing are available for shared environments. Each instance includes an MCP server at /mockserver/mcp. The /mockserver/status and /mockserver/ready probes remain reachable without authentication or authorization.

WireMock simulates APIs and software dependencies so teams can test without live services, exercise edge cases, and build dependent features in parallel. It can match requests using URL patterns, headers, query parameters, cookies, and body content, then return templated responses or simulate delays, network faults, and malformed replies. It can also record interactions with real services and replay them during tests.

The project integrates with JUnit and other testing frameworks, with setup paths for Maven, Gradle, Scala SBT, standalone use, and Docker. Its documented capabilities cover HTTP-based protocols and REST, plus WebSockets, webhooks, HTTPS, gRPC, and GraphQL. WireMock Java is available as a standalone JAR, Docker image, experimental Helm chart, and NPM package; WireMock Cloud is another option. The Free plan costs nothing and includes 1,000 calls per month, one user, three mock APIs, and a 10 requests-per-second limit. Free and trial plans stop running mocks after their API quota is exceeded until the next quota cycle.