diff --git a/tests/core/pyspec/eth2spec/test/altair/block_processing/test_process_sync_committee.py b/tests/core/pyspec/eth2spec/test/altair/block_processing/test_process_sync_committee.py
index e0faf3d0d..9b415cfbd 100644
--- a/tests/core/pyspec/eth2spec/test/altair/block_processing/test_process_sync_committee.py
+++ b/tests/core/pyspec/eth2spec/test/altair/block_processing/test_process_sync_committee.py
@@ -17,7 +17,7 @@ from eth2spec.test.helpers.sync_committee import (
 )
 from eth2spec.test.context import (
     expect_assertion_error,
-    with_all_phases_except,
+    with_altair_and_later,
     with_configs,
     spec_state_test,
     always_bls,
@@ -62,7 +62,7 @@ def get_committee_indices(spec, state, duplicates=False):
         state.randao_mixes[randao_index] = hash(state.randao_mixes[randao_index])
 
 
-@with_all_phases_except([PHASE0])
+@with_altair_and_later
 @spec_state_test
 @always_bls
 def test_invalid_signature_missing_participant(spec, state):
@@ -84,7 +84,7 @@ def test_invalid_signature_missing_participant(spec, state):
     yield from run_sync_committee_processing(spec, state, block, expect_exception=True)
 
 
-@with_all_phases_except([PHASE0])
+@with_altair_and_later
 @spec_state_test
 @always_bls
 def test_invalid_signature_extra_participant(spec, state):
@@ -197,7 +197,7 @@ def run_successful_sync_committee_test(spec, state, committee, committee_bits):
     )
 
 
-@with_all_phases_except([PHASE0])
+@with_altair_and_later
 @with_configs([MINIMAL], reason="to create nonduplicate committee")
 @spec_state_test
 def test_sync_committee_rewards_nonduplicate_committee(spec, state):
@@ -213,7 +213,7 @@ def test_sync_committee_rewards_nonduplicate_committee(spec, state):
     yield from run_successful_sync_committee_test(spec, state, committee, committee_bits)
 
 
-@with_all_phases_except([PHASE0])
+@with_altair_and_later
 @with_configs([MAINNET], reason="to create duplicate committee")
 @spec_state_test
 def test_sync_committee_rewards_duplicate_committee(spec, state):
@@ -229,7 +229,7 @@ def test_sync_committee_rewards_duplicate_committee(spec, state):
     yield from run_successful_sync_committee_test(spec, state, committee, committee_bits)
 
 
-@with_all_phases_except([PHASE0])
+@with_altair_and_later
 @spec_state_test
 @always_bls
 def test_sync_committee_rewards_not_full_participants(spec, state):
@@ -240,7 +240,7 @@ def test_sync_committee_rewards_not_full_participants(spec, state):
     yield from run_successful_sync_committee_test(spec, state, committee, committee_bits)
 
 
-@with_all_phases_except([PHASE0])
+@with_altair_and_later
 @spec_state_test
 @always_bls
 def test_sync_committee_rewards_empty_participants(spec, state):
@@ -250,7 +250,7 @@ def test_sync_committee_rewards_empty_participants(spec, state):
     yield from run_successful_sync_committee_test(spec, state, committee, committee_bits)
 
 
-@with_all_phases_except([PHASE0])
+@with_altair_and_later
 @spec_state_test
 @always_bls
 def test_invalid_signature_past_block(spec, state):
@@ -289,7 +289,7 @@ def test_invalid_signature_past_block(spec, state):
     yield from run_sync_committee_processing(spec, state, invalid_block, expect_exception=True)
 
 
-@with_all_phases_except([PHASE0])
+@with_altair_and_later
 @with_configs([MINIMAL], reason="to produce different committee sets")
 @spec_state_test
 @always_bls
@@ -326,7 +326,7 @@ def test_invalid_signature_previous_committee(spec, state):
     yield from run_sync_committee_processing(spec, state, block, expect_exception=True)
 
 
-@with_all_phases_except([PHASE0])
+@with_altair_and_later
 @spec_state_test
 @always_bls
 @with_configs([MINIMAL], reason="too slow")
diff --git a/tests/core/pyspec/eth2spec/test/altair/epoch_processing/test_process_sync_committee_updates.py b/tests/core/pyspec/eth2spec/test/altair/epoch_processing/test_process_sync_committee_updates.py
index 8ffc51507..c914c476d 100644
--- a/tests/core/pyspec/eth2spec/test/altair/epoch_processing/test_process_sync_committee_updates.py
+++ b/tests/core/pyspec/eth2spec/test/altair/epoch_processing/test_process_sync_committee_updates.py
@@ -2,7 +2,7 @@ from eth2spec.test.context import (
     always_bls,
     spec_state_test,
     spec_test,
-    with_all_phases_except,
+    with_altair_and_later,
     with_configs,
     with_custom_state,
     single_phase,
@@ -49,7 +49,7 @@ def run_sync_committees_progress_test(spec, state):
     assert state.next_sync_committee == third_sync_committee
 
 
-@with_all_phases_except([PHASE0])
+@with_altair_and_later
 @spec_state_test
 @always_bls
 @with_configs([MINIMAL], reason="too slow")
@@ -60,7 +60,7 @@ def test_sync_committees_progress_genesis(spec, state):
     yield from run_sync_committees_progress_test(spec, state)
 
 
-@with_all_phases_except([PHASE0])
+@with_altair_and_later
 @spec_state_test
 @always_bls
 @with_configs([MINIMAL], reason="too slow")
@@ -73,7 +73,7 @@ def test_sync_committees_progress_not_genesis(spec, state):
     yield from run_sync_committees_progress_test(spec, state)
 
 
-@with_all_phases_except([PHASE0])
+@with_altair_and_later
 @with_custom_state(balances_fn=misc_balances, threshold_fn=lambda spec: spec.EJECTION_BALANCE)
 @spec_test
 @single_phase
diff --git a/tests/core/pyspec/eth2spec/test/altair/sanity/test_blocks.py b/tests/core/pyspec/eth2spec/test/altair/sanity/test_blocks.py
index 48ab6956b..ffe743531 100644
--- a/tests/core/pyspec/eth2spec/test/altair/sanity/test_blocks.py
+++ b/tests/core/pyspec/eth2spec/test/altair/sanity/test_blocks.py
@@ -11,9 +11,8 @@ from eth2spec.test.helpers.block import (
 from eth2spec.test.helpers.sync_committee import (
     compute_aggregate_sync_committee_signature,
 )
-from eth2spec.test.helpers.constants import PHASE0
 from eth2spec.test.context import (
-    with_all_phases_except,
+    with_altair_and_later,
     spec_state_test,
 )
 
@@ -40,46 +39,46 @@ def run_sync_committee_sanity_test(spec, state, fraction_full=1.0):
     yield 'post', state
 
 
-@with_all_phases_except([PHASE0])
+@with_altair_and_later
 @spec_state_test
 def test_full_sync_committee_committee(spec, state):
     next_epoch(spec, state)
     yield from run_sync_committee_sanity_test(spec, state, fraction_full=1.0)
 
 
-@with_all_phases_except([PHASE0])
+@with_altair_and_later
 @spec_state_test
 def test_half_sync_committee_committee(spec, state):
     next_epoch(spec, state)
     yield from run_sync_committee_sanity_test(spec, state, fraction_full=0.5)
 
 
-@with_all_phases_except([PHASE0])
+@with_altair_and_later
 @spec_state_test
 def test_empty_sync_committee_committee(spec, state):
     next_epoch(spec, state)
     yield from run_sync_committee_sanity_test(spec, state, fraction_full=0.0)
 
 
-@with_all_phases_except([PHASE0])
+@with_altair_and_later
 @spec_state_test
 def test_full_sync_committee_committee_genesis(spec, state):
     yield from run_sync_committee_sanity_test(spec, state, fraction_full=1.0)
 
 
-@with_all_phases_except([PHASE0])
+@with_altair_and_later
 @spec_state_test
 def test_half_sync_committee_committee_genesis(spec, state):
     yield from run_sync_committee_sanity_test(spec, state, fraction_full=0.5)
 
 
-@with_all_phases_except([PHASE0])
+@with_altair_and_later
 @spec_state_test
 def test_empty_sync_committee_committee_genesis(spec, state):
     yield from run_sync_committee_sanity_test(spec, state, fraction_full=0.0)
 
 
-@with_all_phases_except([PHASE0])
+@with_altair_and_later
 @spec_state_test
 def test_inactivity_scores(spec, state):
     for _ in range(spec.MIN_EPOCHS_TO_INACTIVITY_PENALTY + 2):
diff --git a/tests/core/pyspec/eth2spec/test/altair/unittests/validator/test_validator.py b/tests/core/pyspec/eth2spec/test/altair/unittests/validator/test_validator.py
index 244e1aa7e..e1f5d3860 100644
--- a/tests/core/pyspec/eth2spec/test/altair/unittests/validator/test_validator.py
+++ b/tests/core/pyspec/eth2spec/test/altair/unittests/validator/test_validator.py
@@ -8,7 +8,7 @@ from eth2spec.utils import bls
 from eth2spec.utils.bls import only_with_bls
 from eth2spec.test.context import (
     PHASE0,
-    with_all_phases_except,
+    with_altair_and_later,
     with_state,
 )
 
@@ -25,7 +25,7 @@ def ensure_assignments_in_sync_committee(
         assert spec.is_assigned_to_sync_committee(state, epoch, validator_index)
 
 
-@with_all_phases_except([PHASE0])
+@with_altair_and_later
 @with_state
 def test_is_assigned_to_sync_committee(phases, spec, state):
     epoch = spec.get_current_epoch(state)
@@ -91,7 +91,7 @@ def _get_sync_committee_signature(
 
 
 @only_with_bls()
-@with_all_phases_except([PHASE0])
+@with_altair_and_later
 @with_state
 def test_process_sync_committee_contributions(phases, spec, state):
     # skip over slots at genesis
@@ -144,7 +144,7 @@ def _subnet_for_sync_committee_index(spec, i):
     return i // (spec.SYNC_COMMITTEE_SIZE // spec.SYNC_COMMITTEE_SUBNET_COUNT)
 
 
-@with_all_phases_except([PHASE0])
+@with_altair_and_later
 @with_state
 def test_compute_subnets_for_sync_committee(state, spec, phases):
     some_sync_committee_members = list(
diff --git a/tests/core/pyspec/eth2spec/test/context.py b/tests/core/pyspec/eth2spec/test/context.py
index 65201c0c4..775efdcf3 100644
--- a/tests/core/pyspec/eth2spec/test/context.py
+++ b/tests/core/pyspec/eth2spec/test/context.py
@@ -367,12 +367,20 @@ def with_configs(configs, reason=None):
 
 
 def is_post_altair(spec):
+    if spec.fork == MERGE:  # TODO: remove parallel Altair-Merge condition after rebase.
+        return False
     if spec.fork in FORKS_BEFORE_ALTAIR:
         return False
     return True
 
 
 def is_post_merge(spec):
+    if spec.fork == ALTAIR:  # TODO: remove parallel Altair-Merge condition after rebase.
+        return False
     if spec.fork in FORKS_BEFORE_MERGE:
         return False
     return True
+
+
+with_altair_and_later = with_phases([ALTAIR])  # TODO: include Merge, but not until Merge work is rebased.
+with_merge_and_later = with_phases([MERGE])
diff --git a/tests/core/pyspec/eth2spec/test/helpers/block.py b/tests/core/pyspec/eth2spec/test/helpers/block.py
index 64f406633..41d0a9131 100644
--- a/tests/core/pyspec/eth2spec/test/helpers/block.py
+++ b/tests/core/pyspec/eth2spec/test/helpers/block.py
@@ -96,6 +96,8 @@ def build_empty_block(spec, state, slot=None):
         empty_block.body.sync_aggregate.sync_committee_signature = spec.G2_POINT_AT_INFINITY
 
     if is_post_merge(spec):
+        if not hasattr(state, 'latest_execution_payload_header'):
+            raise Exception("panic!!!")
         empty_block.body.execution_payload = build_empty_execution_payload(spec, state)
 
     apply_randao_reveal(spec, state, empty_block)
diff --git a/tests/core/pyspec/eth2spec/test/merge/block_processing/test_process_execution_payload.py b/tests/core/pyspec/eth2spec/test/merge/block_processing/test_process_execution_payload.py
index f3f521c4b..96a657d7a 100644
--- a/tests/core/pyspec/eth2spec/test/merge/block_processing/test_process_execution_payload.py
+++ b/tests/core/pyspec/eth2spec/test/merge/block_processing/test_process_execution_payload.py
@@ -1,8 +1,5 @@
-from eth2spec.test.helpers.constants import PHASE0, ALTAIR
 from eth2spec.test.helpers.execution_payload import build_empty_execution_payload
-from eth2spec.test.context import spec_state_test, expect_assertion_error, always_bls, with_all_phases_except
-
-with_merge_and_later = with_all_phases_except([PHASE0, ALTAIR])
+from eth2spec.test.context import spec_state_test, expect_assertion_error, always_bls, with_merge_and_later
 
 
 def run_execution_payload_processing(spec, state, execution_payload, valid=True, execution_valid=True):
diff --git a/tests/core/pyspec/eth2spec/test/merge/sanity/test_blocks.py b/tests/core/pyspec/eth2spec/test/merge/sanity/test_blocks.py
index 1f9e69167..4a6db4106 100644
--- a/tests/core/pyspec/eth2spec/test/merge/sanity/test_blocks.py
+++ b/tests/core/pyspec/eth2spec/test/merge/sanity/test_blocks.py
@@ -5,11 +5,11 @@ from eth2spec.test.helpers.block import (
     build_empty_block_for_next_slot
 )
 from eth2spec.test.context import (
-    with_all_phases, spec_state_test
+    with_merge_and_later, spec_state_test
 )
 
 
-@with_all_phases
+@with_merge_and_later
 @spec_state_test
 def test_empty_block_transition(spec, state):
     yield 'pre', state