Implement API to simulate errors in fakeIndexedDB

[bartblast]

Since fakeIndexedDB is used primarily for testing, I propose implementing an API to simulate errors. Due to the asynchronous nature of IndexedDB, most of the code contains error handlers which currently can't be tested.

For example, with this code:

const request = indexedDB.open("my_db", 1);

request.onerror = (event) => {
    throw new MyError("Failed to open database");
};

request.onsuccess = (event) => console.log("All is good!");

It's not possible to test error conditions. The open() function may fail due to many reasons, e.g.:

• Storage limits
• Insufficient permissions
• Database version mismatch
• Concurrent operations
• Cross-origin issues

At the moment, the tests are only able to cover success cases.

Proposed Solution

One possible solution is to set this at the request class level, e.g.:

FDBOpenDBRequest.simulateError(event);

This would allow developers to simulate various error conditions and thoroughly test their error handling code.