Unable to override mock behaviour

[mawkler]

I'm trying to mock an overcomplicated API that I don't own, but that my code makes calls to. For each of my tests I have to mock quite a lot of endpoints, but most of them should behave the same way for all tests. I would therefore like to create a "base mock" that mocks all those endpoints, and then I want to override the base behaviour of one of those endpoints depending on the test.

However, it seems like I can't override the response for a given path if I've already defined it. Here's some code to illustrate the behaviour that I expect:

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

#[tokio::main]
async fn main() {
    let mock_server = MockServer::start().await;

    // Define base behavior
    Mock::given(method("GET"))
        .and(path("/api/base"))
        .respond_with(ResponseTemplate::new(200).set_body_string("Base response"))
        .mount(&mock_server)
        .await;

    // Test 1: Use the base behavior
    let response = reqwest::get(&format!("{}/api/base", &mock_server.uri()))
        .await
        .unwrap();
    assert_eq!(response.text().await.unwrap(), "Base response");

    // Test 2: Override the base behavior
    Mock::given(method("GET"))
        .and(path("/api/base"))
        .respond_with(ResponseTemplate::new(200).set_body_string("Overridden response"))
        .mount(&mock_server)
        .await;

    let response = reqwest::get(&format!("{}/api/base", &mock_server.uri()))
        .await
        .unwrap();

    // This assert fails because we get back "Base response"
    assert_eq!(response.text().await.unwrap(), "Overridden response");
}

Is this expected behaviour? If yes, is there some other way to override the base behaviour?

[LukeMathWalker]

Yes, this isn't currently supported with an "override" semantic. You can limit how many times the base mock matches, but not much more than that.

[mawkler]

I see, thanks for clarifying.

On a side note, thank you very much for writing Zero To Production In Rust! It's an excellent book!

[Raniz85]

This might have been implemented after this issue was opened, but I'm pretty sure this can be achieved with priorities.

Give the base mock a low priority and later mocks will be matched before it.

[mawkler]

Thank you for the suggestion! I was able to get the desired behaviour using .with_priority():

Click to expand

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

#[tokio::main]
async fn main() {
    let mock_server = MockServer::start().await;

    // Define base behavior
    Mock::given(method("GET"))
        .and(path("/api/base"))
        .respond_with(ResponseTemplate::new(200).set_body_string("Base response"))
        .with_priority(6) // <-- I ADDED THIS LINE
        .mount(&mock_server)
        .await;

    // Test 1: Use the base behavior
    let response = reqwest::get(&format!("{}/api/base", &mock_server.uri()))
        .await
        .unwrap();
    assert_eq!(response.text().await.unwrap(), "Base response");

    // Test 2: Override the base behavior
    Mock::given(method("GET"))
        .and(path("/api/base"))
        .respond_with(ResponseTemplate::new(200).set_body_string("Overridden response"))
        .mount(&mock_server)
        .await;

    let response = reqwest::get(&format!("{}/api/base", &mock_server.uri()))
        .await
        .unwrap();

    // This assert fails because we get back "Base response"
    assert_eq!(response.text().await.unwrap(), "Overridden response");
}

See the line with the comment I ADDED THIS LINE.

The priority is 5 by default.