What's the best way to reset the MockPool between tests?

[schaable]

I have a scenario where two tests use the same MockPool. In the first test, I define two interceptors. Let's say that after consuming the first interceptor, I get an assertion error that causes the test to fail. Then, when the second test runs, the unconsumed interceptor from the first test is still present, which could cause issues if I want to make a matching request.

What’s the best way to avoid this? I thought about re-creating the MockAgent between tests, but I’m concerned that might be too resource-intensive. Any recommendations?

EDIT: the scenario described above is just an example. What I want to know is how to handle unconsumed interceptors left over by previous tests.

Example:

const { MockAgent, setGlobalDispatcher, request } = require("undici");
const { before, after, it } = require("node:test");
const assert = require("node:assert");

const mockAgent = new MockAgent({
  keepAliveTimeout: 10,
  keepAliveMaxTimeout: 10,
});
const interceptor = mockAgent.get("http://localhost");
setGlobalDispatcher(mockAgent);

before(() => {
  mockAgent.disableNetConnect();
});

after(() => {
  mockAgent.enableNetConnect();
  mockAgent.close();
});

it("test A", async () => {
  interceptor
    .intercept({
      path: "/path-a",
      method: "GET",
    })
    .reply(200, { foo: "baz" });
  interceptor
    .intercept({
      path: "/path-b",
      method: "GET",
    })
    .reply(200, { hello: "world" });

  let responseA = await request("http://localhost/path-a");
  responseA = await responseA.body.json();
  assert.equal(responseA, { foo: "bar" }); // throws

  // won't run
  let responseB = await request("http://localhost/path-b");
  responseB = await responseB.body.json();
  assert.equal(responseB, { hello: "world" });
});

it("test B", async () => {
  interceptor
    .intercept({
      path: "/path-b",
      method: "GET",
    })
    .reply(200, { dog: "cat" });

  let response = await request("http://localhost/path-b");
  response = await response.body.json();
  // i'm expecting this to be true, but it won't as there's an unconsumed
  // interceptor from test A and will return { hello: "world"}
  assert.equal(response, { dog: "cat" });
});

[metcoder95]

I'd recommend to not re-use the mocks across test scenarios but isolate each scenario, and individually assign their mocks, so scenarios like this can be avoided.

Having global shared mocks (almost) always lead to hard to solve inconsistencies

[schaable]

so, I should re-create the MockAgent before each test that uses interceptors?

[metcoder95]

Yeah, that should be totally fine