diff --git a/src/test/util/setup_common.cpp b/src/test/util/setup_common.cpp
index 9d63aad6721..5ffa7e82ebd 100644
--- a/src/test/util/setup_common.cpp
+++ b/src/test/util/setup_common.cpp
@@ -196,49 +196,34 @@ TestingSetup::~TestingSetup()
 
 TestChain100Setup::TestChain100Setup()
 {
-    // CreateAndProcessBlock() does not support building SegWit blocks, so don't activate in these tests.
-    // TODO: fix the code to support SegWit blocks.
-    gArgs.ForceSetArg("-segwitheight", "432");
-    // Need to recreate chainparams
-    SelectParams(CBaseChainParams::REGTEST);
-
     // Generate a 100-block chain:
     coinbaseKey.MakeNewKey(true);
-    CScript scriptPubKey = CScript() <<  ToByteVector(coinbaseKey.GetPubKey()) << OP_CHECKSIG;
-    for (int i = 0; i < COINBASE_MATURITY; i++)
-    {
+    CScript scriptPubKey = CScript() << ToByteVector(coinbaseKey.GetPubKey()) << OP_CHECKSIG;
+    for (int i = 0; i < COINBASE_MATURITY; i++) {
         std::vector<CMutableTransaction> noTxns;
         CBlock b = CreateAndProcessBlock(noTxns, scriptPubKey);
         m_coinbase_txns.push_back(b.vtx[0]);
     }
 }
 
-// Create a new block with just given transactions, coinbase paying to
-// scriptPubKey, and try to add it to the current chain.
 CBlock TestChain100Setup::CreateAndProcessBlock(const std::vector<CMutableTransaction>& txns, const CScript& scriptPubKey)
 {
     const CChainParams& chainparams = Params();
-    std::unique_ptr<CBlockTemplate> pblocktemplate = BlockAssembler(*m_node.mempool, chainparams).CreateNewBlock(scriptPubKey);
-    CBlock& block = pblocktemplate->block;
+    CTxMemPool empty_pool;
+    CBlock block = BlockAssembler(empty_pool, chainparams).CreateNewBlock(scriptPubKey)->block;
 
-    // Replace mempool-selected txns with just coinbase plus passed-in txns:
-    block.vtx.resize(1);
-    for (const CMutableTransaction& tx : txns)
+    Assert(block.vtx.size() == 1);
+    for (const CMutableTransaction& tx : txns) {
         block.vtx.push_back(MakeTransactionRef(tx));
-    // IncrementExtraNonce creates a valid coinbase and merkleRoot
-    {
-        LOCK(cs_main);
-        unsigned int extraNonce = 0;
-        IncrementExtraNonce(&block, ::ChainActive().Tip(), extraNonce);
     }
+    RegenerateCommitments(block);
 
     while (!CheckProofOfWork(block.GetHash(), block.nBits, chainparams.GetConsensus())) ++block.nNonce;
 
     std::shared_ptr<const CBlock> shared_pblock = std::make_shared<const CBlock>(block);
     Assert(m_node.chainman)->ProcessNewBlock(chainparams, shared_pblock, true, nullptr);
 
-    CBlock result = block;
-    return result;
+    return block;
 }
 
 TestChain100Setup::~TestChain100Setup()
@@ -246,8 +231,8 @@ TestChain100Setup::~TestChain100Setup()
     gArgs.ForceSetArg("-segwitheight", "0");
 }
 
-
-CTxMemPoolEntry TestMemPoolEntryHelper::FromTx(const CMutableTransaction &tx) {
+CTxMemPoolEntry TestMemPoolEntryHelper::FromTx(const CMutableTransaction& tx)
+{
     return FromTx(MakeTransactionRef(tx));
 }
 
diff --git a/src/test/util/setup_common.h b/src/test/util/setup_common.h
index 78b279e42a5..22f5d6d9362 100644
--- a/src/test/util/setup_common.h
+++ b/src/test/util/setup_common.h
@@ -102,15 +102,16 @@ class CBlock;
 struct CMutableTransaction;
 class CScript;
 
-//
-// Testing fixture that pre-creates a
-// 100-block REGTEST-mode block chain
-//
+/**
+ * Testing fixture that pre-creates a 100-block REGTEST-mode block chain
+ */
 struct TestChain100Setup : public RegTestingSetup {
     TestChain100Setup();
 
-    // Create a new block with just given transactions, coinbase paying to
-    // scriptPubKey, and try to add it to the current chain.
+    /**
+     * Create a new block with just given transactions, coinbase paying to
+     * scriptPubKey, and try to add it to the current chain.
+     */
     CBlock CreateAndProcessBlock(const std::vector<CMutableTransaction>& txns,
                                  const CScript& scriptPubKey);