Update testing and restrict to incremental block transitions

specs/phase0/beacon-chain.md

@@ -1219,7 +1219,7 @@ def verify_block_signature(state: BeaconState, signed_block: SignedBeaconBlock)
 
 ```python
 def process_slots(state: BeaconState, slot: Slot) -> None:
-    assert state.slot <= slot
+    assert state.slot < slot
     while state.slot < slot:
         process_slot(state)
         # Process epoch on the start slot of the next epoch

tests/core/pyspec/eth2spec/test/helpers/attestations.py

@@ -243,6 +243,7 @@ def fill_aggregate_attestation(spec, state, attestation, signed=False):
 
 
 def add_attestations_to_state(spec, state, attestations, slot):
+    if state.slot < slot:
         spec.process_slots(state, slot)
     for attestation in attestations:
         spec.process_attestation(state, attestation)

tests/core/pyspec/eth2spec/test/helpers/block.py

@@ -15,6 +15,7 @@ def get_proposer_index_maybe(spec, state, slot, proposer_index=None):
                       " Signing block is slow due to transition for proposer index calculation.")
             # use stub state to get proposer index of future slot
             stub_state = state.copy()
+            if stub_state.slot < slot:
                 spec.process_slots(stub_state, slot)
             proposer_index = spec.get_beacon_proposer_index(stub_state)
     return proposer_index
@@ -52,7 +53,10 @@ def sign_block(spec, state, block, proposer_index=None):
 
 
 def transition_unsigned_block(spec, state, block):
+    if state.slot < block.slot:
         spec.process_slots(state, block.slot)
+    assert state.latest_block_header.slot < block.slot  # There may not already be a block in this slot or past it.
+    assert state.slot == block.slot  # The block must be for this slot
     spec.process_block(state, block)
 
 
@@ -74,6 +78,7 @@ def build_empty_block(spec, state, slot=None):
     if slot < state.slot:
         raise Exception("build_empty_block cannot build blocks for past slots")
     if slot > state.slot:
+        if state.slot < slot:
             # transition forward in copied state to grab relevant data from state
             state = state.copy()
             spec.process_slots(state, slot)

tests/core/pyspec/eth2spec/test/helpers/state.py

@@ -17,6 +17,7 @@ def next_slots(spec, state, slots):
     """
     Transition given slots forward.
     """
+    if slots > 0:
         spec.process_slots(state, state.slot + slots)
 
 
@@ -35,6 +36,7 @@ def next_epoch(spec, state):
     Transition to the start slot of the next epoch
     """
     slot = state.slot + spec.SLOTS_PER_EPOCH - (state.slot % spec.SLOTS_PER_EPOCH)
+    if slot > state.slot:
         spec.process_slots(state, slot)
 
 

tests/core/pyspec/eth2spec/test/phase_0/epoch_processing/run_epoch_process_base.py

@@ -18,6 +18,7 @@ def run_epoch_processing_to(spec, state, process_name: str):
     slot = state.slot + (spec.SLOTS_PER_EPOCH - state.slot % spec.SLOTS_PER_EPOCH)
 
     # transition state to slot before epoch state transition
+    if state.slot < slot - 1:
         spec.process_slots(state, slot - 1)
 
     # start transitioning, do one slot update before the epoch itself.

tests/core/pyspec/eth2spec/test/sanity/test_slots.py

@@ -51,6 +51,7 @@ def test_double_empty_epoch(spec, state):
 @with_all_phases
 @spec_state_test
 def test_over_epoch_boundary(spec, state):
+    if spec.SLOTS_PER_EPOCH > 1:
         spec.process_slots(state, state.slot + (spec.SLOTS_PER_EPOCH // 2))
     yield 'pre', state
     slots = spec.SLOTS_PER_EPOCH