diff --git a/.github/workflows/docker-dist-tests.yml b/.github/workflows/docker-dist-tests.yml
index e6e0973b..5ae2e30a 100644
--- a/.github/workflows/docker-dist-tests.yml
+++ b/.github/workflows/docker-dist-tests.yml
@@ -24,7 +24,7 @@ jobs:
     name: Build and Push
     uses: ./.github/workflows/docker-reusable.yml
     with:
-      nimflags: '-d:disableMarchNative -d:codex_enable_api_debug_peers=true -d:codex_enable_simulated_proof_failures -d:codex_enable_log_counter=true'
+      nimflags: '-d:disableMarchNative -d:codex_enable_api_debug_peers=true -d:codex_enable_proof_failures=true -d:codex_use_hardhat=false -d:codex_enable_log_counter=true'
       nat_ip_auto: true
       tag_latest: ${{ github.ref_name == github.event.repository.default_branch || startsWith(github.ref, 'refs/tags/') }}
       tag_suffix: dist-tests
diff --git a/build.nims b/build.nims
index 037ecd09..568b16f0 100644
--- a/build.nims
+++ b/build.nims
@@ -25,13 +25,13 @@ task codex, "build codex binary":
   buildBinary "codex", params = "-d:chronicles_runtime_filtering -d:chronicles_log_level=TRACE"
 
 task testCodex, "Build & run Codex tests":
-  test "testCodex", params = "-d:codex_testing=true"
+  test "testCodex", params = "-d:codex_enable_proof_failures=true -d:codex_use_hardhat=true"
 
 task testContracts, "Build & run Codex Contract tests":
   test "testContracts"
 
 task testIntegration, "Run integration tests":
-  buildBinary "codex", params = "-d:chronicles_runtime_filtering -d:chronicles_log_level=TRACE -d:codex_testing=true"
+  buildBinary "codex", params = "-d:chronicles_runtime_filtering -d:chronicles_log_level=TRACE -d:codex_enable_proof_failures=true -d:codex_use_hardhat=true"
   test "testIntegration"
 
 task build, "build codex binary":
diff --git a/codex/codex.nim b/codex/codex.nim
index 31ff6053..4fc0f922 100644
--- a/codex/codex.nim
+++ b/codex/codex.nim
@@ -118,7 +118,7 @@ proc bootstrapInteractions(
   if config.persistence:
     # This is used for simulation purposes. Normal nodes won't be compiled with this flag
     # and hence the proof failure will always be 0.
-    when codex_testing:
+    when codex_enable_proof_failures:
       let proofFailures = config.simulateProofFailures
       if proofFailures > 0:
         warn "Enabling proof failure simulation!"
diff --git a/codex/conf.nim b/codex/conf.nim
index 019f0c41..4a0e70f4 100644
--- a/codex/conf.nim
+++ b/codex/conf.nim
@@ -44,7 +44,8 @@ export net, DefaultQuotaBytes, DefaultBlockTtl, DefaultBlockMaintenanceInterval,
 
 const
   codex_enable_api_debug_peers* {.booldefine.} = false
-  codex_testing* {.booldefine.} = false
+  codex_enable_proof_failures* {.booldefine.} = false
+  codex_use_hardhat* {.booldefine.} = false
   codex_enable_log_counter* {.booldefine.} = false
 
 type
diff --git a/codex/contracts/clock.nim b/codex/contracts/clock.nim
index 4c6b5fd5..26d2d263 100644
--- a/codex/contracts/clock.nim
+++ b/codex/contracts/clock.nim
@@ -23,7 +23,6 @@ proc new*(_: type OnChainClock, provider: Provider): OnChainClock =
 method start*(clock: OnChainClock) {.async.} =
   if clock.started:
     return
-  clock.started = true
 
   proc onBlock(blck: Block) {.upraises:[].} =
     clock.lastBlockTime = blck.timestamp
@@ -33,16 +32,17 @@ method start*(clock: OnChainClock) {.async.} =
     onBlock(latestBlock)
 
   clock.subscription = await clock.provider.subscribe(onBlock)
+  clock.started = true
 
 method stop*(clock: OnChainClock) {.async.} =
   if not clock.started:
     return
-  clock.started = false
 
   await clock.subscription.unsubscribe()
+  clock.started = false
 
 method now*(clock: OnChainClock): SecondsSince1970 =
-  when codex_testing:
+  when codex_use_hardhat:
     # hardhat's latest block.timestamp is usually 1s behind the block timestamp
     # in the newHeads event. When testing, always return the latest block.
     try:
@@ -56,6 +56,7 @@ method now*(clock: OnChainClock): SecondsSince1970 =
       return clock.lastBlockTime.truncate(int64)
 
   else:
+    doAssert clock.started, "clock should be started before calling now()"
     trace "using cached block timestamp (newHeads) for clock.now",
       timestamp = clock.lastBlockTime.truncate(int64)
     return clock.lastBlockTime.truncate(int64)
diff --git a/codex/sales/states/filled.nim b/codex/sales/states/filled.nim
index 4fe551fd..c5bc4c27 100644
--- a/codex/sales/states/filled.nim
+++ b/codex/sales/states/filled.nim
@@ -51,7 +51,7 @@ method run*(state: SaleFilled, machine: Machine): Future[?State] {.async.} =
     if err =? (await onExpiryUpdate(request.content.cid, requestEnd)).errorOption:
       return some State(SaleErrored(error: err))
 
-    when codex_testing:
+    when codex_enable_proof_failures:
       if context.simulateProofFailures > 0:
         info "Proving with failure rate", rate = context.simulateProofFailures
         return some State(SaleProvingSimulated(failEveryNProofs: context.simulateProofFailures))
diff --git a/codex/sales/states/provingsimulated.nim b/codex/sales/states/provingsimulated.nim
index b0ae7206..f5753cf2 100644
--- a/codex/sales/states/provingsimulated.nim
+++ b/codex/sales/states/provingsimulated.nim
@@ -1,5 +1,5 @@
 import ../../conf
-when codex_testing:
+when codex_enable_proof_failures:
   import std/strutils
   import pkg/chronicles
   import pkg/stint
diff --git a/config.nims b/config.nims
index 3acc58b5..a93d958c 100644
--- a/config.nims
+++ b/config.nims
@@ -95,8 +95,6 @@ if not defined(macosx):
     --define:nimStackTraceOverride
     switch("import", "libbacktrace")
 
-switch("define", "codex_testing=true")
-
 # `switch("warning[CaseTransition]", "off")` fails with "Error: invalid command line option: '--warning[CaseTransition]'"
 switch("warning", "CaseTransition:off")