Add new process pending deposits test

tests/core/pyspec/eth2spec/test/electra/epoch_processing/pending_deposits/test_process_pending_deposits.py

@@ -333,6 +333,34 @@ def test_process_pending_deposits_multiple_pending_deposits_above_churn(spec, st
     ]
 
 
+@with_electra_and_later
+@spec_state_test
+def test_process_pending_deposits_multiple_for_new_validator(spec, state):
+    """
+    - There are three pending deposits in the state, all pointing to the same public key.
+    - The public key does not exist in the beacon state.
+    - The first pending deposit has an invalid signature and should be ignored.
+    - The second pending deposit has a valid signature and the validator should be created.
+    - The third pending deposit has a valid signature and should be applied.
+    """
+    # A new validator, pubkey doesn't exist in the state
+    validator_index = len(state.validators)
+    amount = spec.EFFECTIVE_BALANCE_INCREMENT
+
+    # Add pending deposits to the state
+    # Provide different amounts so we can tell which were applied
+    state.pending_deposits.append(prepare_pending_deposit(spec, validator_index, amount * 1, signed=False))
+    state.pending_deposits.append(prepare_pending_deposit(spec, validator_index, amount * 2, signed=True))
+    state.pending_deposits.append(prepare_pending_deposit(spec, validator_index, amount * 4, signed=True))
+
+    yield from run_process_pending_deposits(spec, state)
+
+    # The second and third deposits were applied
+    assert state.balances[validator_index] == amount * 6
+    # No more pending deposits
+    assert state.pending_deposits == []
+
+
 @with_electra_and_later
 @spec_state_test
 def test_process_pending_deposits_skipped_deposit_exiting_validator(spec, state):