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✓ Uses Rust 2018 edition

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0.1.0 Apr 13, 2020

#96 in Development tools

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HTTP mocking to test Rust applications.

wiremock provides HTTP mocking to perform black-box testing of Rust applications that interact with third-party APIs.

It provides mocking of HTTP responses using request matching and response templating.

The name wiremock is a reference to WireMock.Net, a .NET port of the original Wiremock from Java.

Table of Contents

  1. Getting started
  2. Matchers
  3. Spying
  4. Test isolation
  5. Runtime compatibility
  6. Prior art
  7. Future evolution
  8. License

Getting started

use wiremock::{MockServer, Mock, ResponseTemplate};
use wiremock::matchers::{method, path};

async fn main() {
    // Start a background HTTP server on a random local port
    let mock_server = MockServer::start().await;

    // Arrange the behaviour of the MockServer adding a Mock:
    // when it receives a GET request on '/hello' it will respond with a 200.
        // Mounting the mock on the mock server - it's now effective!
    // If we probe the MockServer using any HTTP client it behaves as expected.
    let status = surf::get(format!("{}/hello", &mock_server.uri()))
    assert_eq!(status.as_u16(), 200);

    // If the request doesn't match any `Mock` mounted on our `MockServer` a 404 is returned.
    let status = surf::get(format!("{}/missing", &mock_server.uri()))
    assert_eq!(status.as_u16(), 404);


wiremock provides a set of matching strategies out of the box - check the matchers module for a complete list.

You can define your own matchers using the Match trait, as well as using Fn closures.
Check Match's documentation for more details and examples.


wiremock empowers you to set expectations on the number of invocations to your Mocks - check the expect method for more details.

Expectations can be used to verify that a side-effect has (or has not) taken place!

Expectations are automatically verified during the shutdown of each MockServer instance, at the end of your test. A failed verification will trigger a panic.
By default, no expectations are set on your Mocks.

Test isolation

Each instance of MockServer is fully isolated: start takes care of finding a random port available on your local machine which is assigned to the new MockServer.

You should use one instance of MockServer for each test, to ensure full isolation and no cross-test interference.

When a MockServer instance goes out of scope (e.g. the test finishes), the corresponding HTTP server running in the background is shut down to free up the port it was using.

Runtime compatibility

wiremock can be used (and it is tested to work) with both async_std and tokio as futures runtimes.
If you encounter any compatibility bug, please open an issue on our GitHub repository.

Prior art

mockito and httpmock provide HTTP mocking for Rust.

Check the table below to see how wiremock compares to them across the following dimensions:

  • Test execution strategy (do tests have to be executed sequentially or can they be executed in parallel?);
  • How many APIs can I mock in a test?
  • Out-of-the-box request matchers;
  • Extensible request matching (i.e. you can define your own matchers);
  • Sync/Async API;
  • Spying (e.g. verify that a mock has/hasn't been called in a test);
  • Standalone mode (i.e. can I launch an HTTP mock server outside of a test suite?).
Test execution strategy How many APIs can I mock? Out-of-the-box request matchers Extensible request maching API Spying Standalone mode
mockito ❌ Sequential ❌ 1 Sync
httpmock ❌ Sequential ❌ 1 Sync
wiremock ✔ Parallel ️ ✔ Unbounded Async

Future evolution

More request matchers can be added to those provided out-of-the-box to handle common usecases.


Licensed under either of Apache License, Version 2.0 or MIT license at your option.
Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in this crate by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.


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