After Angular 13 Upgrade, Jasmine Unit Test Fails - Expected one matching request for criteria "Match method: POST, URL: api/x/x-search", found none

Question

After upgrading to Angular 13 from 12, some of the Unit Tests started failing:

Error: Expected one matching request for criteria "Match method: POST, URL: api/x/x-search", found none.

This is the mock

async function mockXSearch(error?: string) {

const req = httpMock.expectOne({ method: 'POST', url: 'api/x/x-search' });
    if (error) {
      req.flush({ title: errorMsg }, { status: 500, statusText: 'Internal Server Error' });
    } else {
      req.flush(mockX, { status: 200, statusText: 'OK' });
    }
    return page.whenStable();
}

And this is the service:

searchX(someData: string, foo: number, xType: XType) {
    return this.http.post<X[]>(`${this.baseUrl}/x-search`, { someData, foo, xType });
}

I already checked that the Mock Url and the Service Url make match. Any idea ?