diff --git a/test_libs/pyspec/eth2spec/test/context.py b/test_libs/pyspec/eth2spec/test/context.py
index d3d9be588..b2e67d761 100644
--- a/test_libs/pyspec/eth2spec/test/context.py
+++ b/test_libs/pyspec/eth2spec/test/context.py
@@ -6,7 +6,7 @@ from .helpers.genesis import create_genesis_state
 from .utils import spectest, with_args
 
 # Provides a genesis state as first argument to the function decorated with this
-with_state = with_args(lambda: [create_genesis_state(spec.SHARD_COUNT * 2)])
+with_state = with_args(lambda: [create_genesis_state(spec.SLOTS_PER_EPOCH * 8)])
 
 
 # shorthand for decorating @with_state @spectest()
diff --git a/test_libs/pyspec/eth2spec/test/helpers/attestations.py b/test_libs/pyspec/eth2spec/test/helpers/attestations.py
index 9e00489a7..7164cf160 100644
--- a/test_libs/pyspec/eth2spec/test/helpers/attestations.py
+++ b/test_libs/pyspec/eth2spec/test/helpers/attestations.py
@@ -6,8 +6,9 @@ from eth2spec.phase0.spec import (
     Attestation,
     AttestationData,
     AttestationDataAndCustodyBit,
-    get_epoch_start_slot, get_block_root, get_current_epoch, get_previous_epoch, slot_to_epoch, get_shard_delta,
-    get_crosslink_committee, get_domain, IndexedAttestation, get_attesting_indices, BeaconState, get_block_root_at_slot)
+    get_epoch_start_slot, get_block_root, get_current_epoch, get_previous_epoch, slot_to_epoch,
+    get_crosslink_committee, get_domain, IndexedAttestation, get_attesting_indices, BeaconState, get_block_root_at_slot,
+    get_epoch_start_shard, get_epoch_committee_count)
 from eth2spec.phase0.state_transition import (
     state_transition, state_transition_to
 )
@@ -59,11 +60,10 @@ def get_valid_attestation(state, slot=None, signed=False):
     if slot is None:
         slot = state.slot
 
-    if slot_to_epoch(slot) == get_current_epoch(state):
-        shard = (state.latest_start_shard + slot) % spec.SLOTS_PER_EPOCH
-    else:
-        previous_shard_delta = get_shard_delta(state, get_previous_epoch(state))
-        shard = (state.latest_start_shard - previous_shard_delta + slot) % spec.SHARD_COUNT
+    epoch = slot_to_epoch(slot)
+    epoch_start_shard = get_epoch_start_shard(state, epoch)
+    committees_per_slot = get_epoch_committee_count(state, epoch) // spec.SLOTS_PER_EPOCH
+    shard = (epoch_start_shard + committees_per_slot * (slot % spec.SLOTS_PER_EPOCH)) % spec.SHARD_COUNT
 
     attestation_data = build_attestation_data(state, slot, shard)
 
diff --git a/test_libs/pyspec/eth2spec/test/helpers/keys.py b/test_libs/pyspec/eth2spec/test/helpers/keys.py
index f59fbb159..f47cd7c10 100644
--- a/test_libs/pyspec/eth2spec/test/helpers/keys.py
+++ b/test_libs/pyspec/eth2spec/test/helpers/keys.py
@@ -1,6 +1,6 @@
 from py_ecc import bls
 from eth2spec.phase0 import spec
 
-privkeys = [i + 1 for i in range(spec.SHARD_COUNT * 8)]
+privkeys = [i + 1 for i in range(spec.SLOTS_PER_EPOCH * 16)]
 pubkeys = [bls.privtopub(privkey) for privkey in privkeys]
 pubkey_to_privkey = {pubkey: privkey for privkey, pubkey in zip(privkeys, pubkeys)}