kvnemesis: add another buffered-writes variant

Until we are confident in the lock durability upgrading code, let's
test in its absence. This will also ensure we are losing locks at some
rate and stress the new lock-loss detection.

Epic: none
Release note: None

Author: stevendanna

pkg/kv/kvnemesis/kvnemesis_test.go

@@ -330,9 +330,32 @@ func TestKVNemesisSingleNode_ReproposalChaos(t *testing.T) {
 	})
 }
 
-// TestKVNemesisMultiNode_BufferedWrites runs KVNemesis with write buffering
-// enabled.
-func TestKVNemesisMultiNode_BufferedWrites(t *testing.T) {
+// TestKVNemesisMultiNode_BufferedWritesNoLockDurabilityUpgrades runs KVNemesis
+// with write buffering enabled and no lock durability ugprades. We leave splits
+// to be metamorphic since those are all handled in-memory.
+func TestKVNemesisMultiNode_BufferedWritesNoLockDurabilityUpgrades(t *testing.T) {
+	defer leaktest.AfterTest(t)()
+	defer log.Scope(t).Close(t)
+
+	testKVNemesisImpl(t, kvnemesisTestCfg{
+		numNodes:                     3,
+		numSteps:                     defaultNumSteps,
+		concurrency:                  5,
+		seedOverride:                 0,
+		invalidLeaseAppliedIndexProb: 0.2,
+		injectReproposalErrorProb:    0.2,
+		assertRaftApply:              true,
+		bufferedWriteProb:            0.70,
+		testSettings: func(ctx context.Context, st *cluster.Settings) {
+			concurrency.UnreplicatedLockReliabilityLeaseTransfer.Override(ctx, &st.SV, false)
+			concurrency.UnreplicatedLockReliabilityMerge.Override(ctx, &st.SV, false)
+			kvcoord.BufferedWritesEnabled.Override(ctx, &st.SV, true)
+		}})
+}
+
+// TestKVNemesisMultiNode_BufferedWritesLockDurabilityUpgrades tests buffered
+// writes with all lock durability features enabled.
+func TestKVNemesisMultiNode_BufferedWritesLockDurabilityUpgrades(t *testing.T) {
 	defer leaktest.AfterTest(t)()
 	defer log.Scope(t).Close(t)