Provide a way to steer the router state machine during integration tests.

[o0Ignition0o]

This changeset provides a new TestRouterHttpServer with a couple of interesting functions for us to write "semi" integrated tests.

Why?

This will allow us to make sure the router updates as expected if configuration, schema and entitlements change.

Ok this sounds great but how do I...

Create a TestRouterHttpServer?

Add your test to apollo-router/src/router.rs:

    #[tokio::test(flavor = "multi_thread")]
    async fn basic_event_stream_test() {
        let mut router_handle = TestRouterHttpServer::new();
   }

Get the router to start?

It will need a valid configuration, a valid schema, and valid entitlements:

      let configuration =
            Configuration::from_str(include_str!("testdata/supergraph_config.router.yaml"))
                .unwrap();
        let schema = include_str!("testdata/supergraph.graphql");

        router_handle
            .send_event(UpdateConfiguration(configuration))
            .await
            .unwrap();
        router_handle
            .send_event(UpdateSchema(schema.to_string()))
            .await
            .unwrap();
        router_handle
            .send_event(UpdateEntitlement(EntitlementState::Unentitled))
            .await
            .unwrap();

Send requests to the router?

        let request = Request::builder().query(r#"{ me { username } }"#).build();

        let response = router_handle.request(request).await.unwrap();
        assert_eq!(
            "@ada",
            response
                .data
                .unwrap()
                .get("me")
                .unwrap()
                .get("username")
                .unwrap()
        );

Get the router to shut down once my tests have passed ?

        router_handle.shutdown().await.unwrap();

You can now have fine grained control over the sequence of events that are processed by the router, and write the relevant regression tests.

That's it! No more excuses!