diff --git a/tests/core/pyspec/eth2spec/test/helpers/constants.py b/tests/core/pyspec/eth2spec/test/helpers/constants.py
index ccd7b20a2..d8f2a37ba 100644
--- a/tests/core/pyspec/eth2spec/test/helpers/constants.py
+++ b/tests/core/pyspec/eth2spec/test/helpers/constants.py
@@ -7,21 +7,24 @@ from .typing import SpecForkName, ConfigName
 # Some of the Spec module functionality is exposed here to deal with phase-specific changes.
 PHASE0 = SpecForkName('phase0')
 ALTAIR = SpecForkName('altair')
+MERGE = SpecForkName('merge')
 
 # Experimental phases (not included in default "ALL_PHASES"):
-MERGE = SpecForkName('merge')
 SHARDING = SpecForkName('sharding')
 CUSTODY_GAME = SpecForkName('custody_game')
 DAS = SpecForkName('das')
 
 # The forks that pytest runs with.
-ALL_PHASES = (PHASE0, ALTAIR)
+ALL_PHASES = (PHASE0, ALTAIR, MERGE)
 # The forks that output to the test vectors.
-TESTGEN_FORKS = (PHASE0, ALTAIR)
+TESTGEN_FORKS = (PHASE0, ALTAIR, MERGE)
 # TODO: everything runs in parallel to Altair.
 # After features are rebased on the Altair fork, this can be reduced to just PHASE0.
 FORKS_BEFORE_ALTAIR = (PHASE0, MERGE, SHARDING, CUSTODY_GAME, DAS)
 
+# TODO: when rebasing Merge onto Altair, add ALTAIR to this tuple.
+FORKS_BEFORE_MERGE = (PHASE0,)
+
 #
 # Config
 #