refactor: Enable stricter test linting

test/unit/util/locking/FileSystemResourceLocker.test.ts

@@ -125,7 +125,7 @@ describe('A FileSystemResourceLocker', (): void => {
   it('stops proper-lock from throwing errors after finalize was called.', async(): Promise<void> => {
     // Tests should never access private fields so we need to change this after splitting the test as mentioned above.
     // Once we have a mock we can check which parameters `unlock` was called with and extract the function from there.
-    expect((): void => (locker as any).customOnCompromised(new Error('test'))).toThrow();
+    expect((): void => (locker as any).customOnCompromised(new Error('test'))).toThrow('test');
     await locker.finalize();
     expect((locker as any).customOnCompromised(new Error('test'))).toBeUndefined();
   });

test/unit/util/locking/GreedyReadWriteLocker.test.ts

@@ -36,7 +36,7 @@ describe('A GreedyReadWriteLocker', (): void => {
   });
 
   it('errors if the read counter has an unexpected value.', async(): Promise<void> => {
-    storage.get = jest.fn().mockResolvedValue(0);
+    jest.spyOn(storage, 'get').mockResolvedValue(0);
     await expect(locker.withReadLock(resourceId, (): number => 5)).rejects.toThrow(InternalServerError);
   });
 });