diff --git a/beacon_chain.nimble b/beacon_chain.nimble
index 055b0a302..e9dd79323 100644
--- a/beacon_chain.nimble
+++ b/beacon_chain.nimble
@@ -57,6 +57,9 @@ task test, "Run all tests":
   #buildBinary "test_fixture_ssz_static", "tests/official/", "-r -d:release -d:chronicles_log_level=DEBUG -d:const_preset=minimal"
   #buildBinary "test_fixture_ssz_static", "tests/official/", "-r -d:release -d:chronicles_log_level=DEBUG -d:const_preset=mainnet"
 
+  buildBinary "working_tests", "tests/", "-r -d:release -d:chronicles_log_level=DEBUG -d:const_preset=minimal"
+  buildBinary "working_tests", "tests/", "-r -d:release -d:chronicles_log_level=DEBUG -d:const_preset=mainnet"
+
   #buildBinary "all_fixtures_require_ssz", "tests/official/", "-r -d:release -d:chronicles_log_level=DEBUG -d:const_preset=minimal"
   #buildBinary "all_fixtures_require_ssz", "tests/official/", "-r -d:release -d:chronicles_log_level=DEBUG -d:const_preset=mainnet"
 
diff --git a/beacon_chain/spec/beaconstate.nim b/beacon_chain/spec/beaconstate.nim
index ad1b6146f..3053ad8ae 100644
--- a/beacon_chain/spec/beaconstate.nim
+++ b/beacon_chain/spec/beaconstate.nim
@@ -11,7 +11,7 @@ import
   ../extras, ../ssz,
   ./crypto, ./datatypes, ./digest, ./helpers, ./validator
 
-# https://github.com/ethereum/eth2.0-specs/blob/v0.8.4/specs/core/0_beacon-chain.md#is_valid_merkle_branch
+# https://github.com/ethereum/eth2.0-specs/blob/v0.9.0/specs/core/0_beacon-chain.md#is_valid_merkle_branch
 func is_valid_merkle_branch(leaf: Eth2Digest, branch: openarray[Eth2Digest], depth: uint64, index: uint64, root: Eth2Digest): bool =
   ## Check if ``leaf`` at ``index`` verifies against the Merkle ``root`` and
   ## ``branch``.
@@ -489,7 +489,7 @@ func get_indexed_attestation*(state: BeaconState, attestation: Attestation,
     signature: attestation.signature,
   )
 
-# https://github.com/ethereum/eth2.0-specs/blob/v0.8.4/specs/core/0_beacon-chain.md#attestations
+# https://github.com/ethereum/eth2.0-specs/blob/v0.9.0/specs/core/0_beacon-chain.md#attestations
 proc check_attestation*(
     state: BeaconState, attestation: Attestation, flags: UpdateFlags,
     stateCache: var StateCache): bool =
@@ -511,35 +511,32 @@ proc check_attestation*(
     warn("Target epoch not current or previous epoch")
     return
 
-  let attestation_slot = get_attestation_data_slot(state, attestation.data)
-
-  if not (attestation_slot + MIN_ATTESTATION_INCLUSION_DELAY <= stateSlot):
+  if not (data.slot + MIN_ATTESTATION_INCLUSION_DELAY <= stateSlot):
     warn("Attestation too new",
-      attestation_slot = shortLog(attestation_slot),
+      attestation_slot = shortLog(data.slot),
       state_slot = shortLog(stateSlot))
     return
 
-  if not (stateSlot <= attestation_slot + SLOTS_PER_EPOCH):
+  if not (stateSlot <= data.slot + SLOTS_PER_EPOCH):
     warn("Attestation too old",
-      attestation_slot = shortLog(attestation_slot),
+      attestation_slot = shortLog(data.slot),
       state_slot = shortLog(stateSlot))
     return
 
-  #let committee = get_crosslink_committee(state, data.target.epoch, data.crosslink.shard, stateCache)
-  #if attestation.aggregation_bits.len != attestation.custody_bits.len:
-  #  warn("Inconsistent aggregation and custody bits",
-  #    aggregation_bits_len = attestation.aggregation_bits.len,
-  #    custody_bits_len = attestation.custody_bits.len
-  #  )
-  #  return
-  #if attestation.aggregation_bits.len != committee.len:
-  #  warn("Inconsistent aggregation and committee length",
-  #    aggregation_bits_len = attestation.aggregation_bits.len,
-  #    committee_len = committee.len
-  #  )
-  #  return
+  let committee = get_beacon_committee(state, data.slot, data.index, stateCache)
+  if attestation.aggregation_bits.len != attestation.custody_bits.len:
+    warn("Inconsistent aggregation and custody bits",
+      aggregation_bits_len = attestation.aggregation_bits.len,
+      custody_bits_len = attestation.custody_bits.len
+    )
+    return
+  if attestation.aggregation_bits.len != committee.len:
+    warn("Inconsistent aggregation and committee length",
+      aggregation_bits_len = attestation.aggregation_bits.len,
+      committee_len = committee.len
+    )
+    return
 
-  # Check FFG data, crosslink data, and signature
   let ffg_check_data = (data.source.epoch, data.source.root, data.target.epoch)
 
   if data.target.epoch == get_current_epoch(state):
@@ -553,7 +550,6 @@ proc check_attestation*(
       warn("FFG data not matching current justified epoch")
       return
 
-  # Check signature
   if not is_valid_indexed_attestation(
       state, get_indexed_attestation(state, attestation, stateCache)):
     warn("process_attestation: signature or bitfields incorrect")
diff --git a/beacon_chain/spec/presets/minimal.nim b/beacon_chain/spec/presets/minimal.nim
index 71b6623aa..da6f9bf1c 100644
--- a/beacon_chain/spec/presets/minimal.nim
+++ b/beacon_chain/spec/presets/minimal.nim
@@ -22,19 +22,21 @@ const
   # ---------------------------------------------------------------
   # https://github.com/ethereum/eth2.0-specs/blob/v0.8.4/configs/minimal.yaml#L4
 
-  # Changed
+  # TODO remove
   SHARD_COUNT* {.intdefine.} = 8
+
+  # Changed
   MAX_COMMITTEES_PER_SLOT* = 4
   TARGET_COMMITTEE_SIZE* = 4
 
   # Unchanged
-  MAX_VALIDATORS_PER_COMMITTEE* = 4096
+  MAX_VALIDATORS_PER_COMMITTEE* = 2048
   MIN_PER_EPOCH_CHURN_LIMIT* = 4
   CHURN_LIMIT_QUOTIENT* = 2^16
 
   # Changed
   SHUFFLE_ROUND_COUNT* = 10
-  MIN_GENESIS_ACTIVE_VALIDATOR_COUNT* {.intdefine.} = 99
+  MIN_GENESIS_ACTIVE_VALIDATOR_COUNT* {.intdefine.} = 64
   MIN_GENESIS_TIME* {.intdefine.} = 0
 
   # Constants
diff --git a/beacon_chain/spec/state_transition_epoch.nim b/beacon_chain/spec/state_transition_epoch.nim
index 8d08d7cd1..6ea9eee3b 100644
--- a/beacon_chain/spec/state_transition_epoch.nim
+++ b/beacon_chain/spec/state_transition_epoch.nim
@@ -92,7 +92,7 @@ func get_attesting_balance(
   get_total_balance(state, get_unslashed_attesting_indices(
     state, attestations, stateCache))
 
-# https://github.com/ethereum/eth2.0-specs/blob/v0.8.4/specs/core/0_beacon-chain.md#justification-and-finalization
+# https://github.com/ethereum/eth2.0-specs/blob/v0.9.0/specs/core/0_beacon-chain.md#justification-and-finalization
 proc process_justification_and_finalization*(
     state: var BeaconState, stateCache: var StateCache) =
 
@@ -326,7 +326,7 @@ func get_attestation_deltas(state: BeaconState, stateCache: var StateCache):
 
   (rewards, penalties)
 
-# https://github.com/ethereum/eth2.0-specs/blob/v0.8.4/specs/core/0_beacon-chain.md#rewards-and-penalties-1
+# https://github.com/ethereum/eth2.0-specs/blob/v0.9.0/specs/core/0_beacon-chain.md#rewards-and-penalties-1
 func process_rewards_and_penalties(
     state: var BeaconState, cache: var StateCache) =
   if get_current_epoch(state) == GENESIS_EPOCH:
diff --git a/tests/working_tests.nim b/tests/working_tests.nim
new file mode 100644
index 000000000..30bbc6357
--- /dev/null
+++ b/tests/working_tests.nim
@@ -0,0 +1,11 @@
+import
+  official/test_fixture_bls,
+  official/test_fixture_shuffling,
+  official/test_fixture_ssz_generic_types,
+  official/test_fixture_sanity_slots,
+  official/test_fixture_operations_voluntary_exit,
+  official/test_fixture_ssz_uint,
+  official/test_fixture_operations_deposits,
+  spec_block_processing/test_process_attestation.nim,
+  spec_block_processing/test_process_deposits.nim,
+  spec_epoch_processing/test_process_justification_and_finalization