Unit Testing Passport Strategy / NestJS Guard - unit-testing

Question

I have a JWTGuard() decorator which follows the implementation as described in https://docs.nestjs.com/security/authentication#jwt-functionality
It looks like so:
import { ExecutionContext, Injectable } from '#nestjs/common';
import { Reflector } from '#nestjs/core';
import { AuthGuard } from '#nestjs/passport';
import { IS_PUBLIC_ROUTE } from '../decorators/public-route.decorator';
#Injectable()
export class JWTAuthenticationGuard extends AuthGuard('jwt') {
constructor(private readonly reflector: Reflector) {
super();
}
canActivate(context: ExecutionContext): Promise<boolean> {
const isPublic = this.reflector.getAllAndOverride<boolean>(
IS_PUBLIC_ROUTE,
[context.getHandler(), context.getClass()],
);
if (isPublic) return true;
return super.canActivate(context)
}
}
It works as expected, but having difficulty unit testing the guard. In short, I want to test three things:
If IS_PUBLIC_ROUTE is set, then canActivate() returns true ✅ this unit test works
If an expired/invalid/incorrectly signed token is passed, canActivate() returns false ❌
If a valid token is found, canActivate() returns true ❌
I tried to follow https://github.com/jmcdo29/testing-nestjs/blob/master/apps/complex-sample/src/cat/cat.guard.spec.ts which just tests a bare guard, not extending a Passport Guard.
Tests are setup as follows:
let guard: JWTAuthenticationGuard;
const reflector = new Reflector();
beforeEach(() => {
guard = new JWTAuthenticationGuard(reflector);
passport.use('jwt', new JWTStrategy());
});
The first test (should return false)
it('should return false if no authorization token is found', () => {
const context = createMock<ExecutionContext>();
const result = guard.canActivate(context);
expect(result).toBe(false);
});
My test never even makes it to the expect() clause, as it has thrown an UnauthorisedException and the test suite exits entirely.
I tried debugging inside the canActivate() method, and checking the type of super.canActivate() which tells me that it's a pending promise. I tried awaiting it, but still says its Pending, I tried wrapping in a try/catch, but the catch block never runs. Reading through the code of passport's AuthGuard, it never throws either.
I tried to add a valid token:
it('should return false if no authorization token is found', async () => {
const context = createMock<ExecutionContext>();
expect(context.switchToHttp()).toBeDefined();
context.switchToHttp().getRequest.mockReturnValue({
headers: {
Authorization:
'Bearer ey...[truncated]...dE',
},
});
const result = await guard.canActivate(context);
expect(result).toBe(true);
however I still just get an UnauthorisedException thrown from god knows where at the result = guard.can... line, and still never makes it to the expect.
Any guidance would be appriciated.