Replace datasource in test environment for Loopback - node.js

Question

The default acceptance test for PingController created on project startup fails because my application has a Postgresql datasource that is not reachable in test environment. I try to replace this datasource by one in memory but it doesn't work, it still uses the "real" one.
I changed the setupApplication method this way :
export async function setupApplication(): Promise<AppWithClient> {
const restConfig = givenHttpServerConfig({
});
const app = new MyApplication({
rest: restConfig,
});
const datasource = new juggler.DataSource({
name: 'myds',
connector: 'memory',
});
app.bind('datasources.myds').to(datasource);
await app.boot();
await app.start();
const client = createRestAppClient(app);
return {app, client};
}
What am I doing wrong ?
Tanks for your help.

Answer 1

app.boot() scans the project root for artifacts and will override the bindings.
For unit tests or tests that are limited to only a few components, it's preferred to remove app.boot() and then explicitly bind each artifact that's required for that test. This will make it easier to detect unexpected artifact dependencies.
Otherwise, ensure that app.boot() is called before any manual bindings:
export async function setupApplication(): Promise<AppWithClient> {
const restConfig = givenHttpServerConfig({
});
const app = new MyApplication({
rest: restConfig,
});
const datasource = new juggler.DataSource({
name: 'myds',
connector: 'memory',
});
await app.boot();
// Move manual bindings after `app.boot()`
app.bind('datasources.myds').to(datasource);
await app.start();
const client = createRestAppClient(app);
return {app, client};
}