asim: add random predefined cluster config selection

This patch takes the first step towards a randomized framework by enabling asim
testing to randomly select a cluster information configuration from a set of
predefined choices. These choices are hardcoded and represent common cluster
configurations.

Part of: #106311
Release note: None

pkg/kv/kvserver/asim/tests/BUILD.bazel

@@ -35,7 +35,7 @@ go_library(
         "assert.go",
         "default_settings.go",
         "rand_framework.go",
-        "rand_settings.go",
+        "rand_gen.go",
     ],
     importpath = "github.com/cockroachdb/cockroach/pkg/kv/kvserver/asim/tests",
     visibility = ["//visibility:public"],
@@ -45,6 +45,7 @@ go_library(
         "//pkg/kv/kvserver/asim/event",
         "//pkg/kv/kvserver/asim/gen",
         "//pkg/kv/kvserver/asim/metrics",
+        "//pkg/kv/kvserver/asim/state",
         "//pkg/roachpb",
         "//pkg/spanconfig/spanconfigtestutils",
         "//pkg/util/log",

pkg/kv/kvserver/asim/tests/rand_framework.go

@@ -58,7 +58,7 @@ func (f randTestingFramework) getCluster() gen.ClusterGen {
 	if !f.s.randOptions["cluster"] {
 		return defaultBasicClusterGen()
 	}
-	return gen.BasicCluster{}
+	return f.randomClusterInfoGen(f.s.randSource)
 }
 
 func (f randTestingFramework) getRanges() gen.RangeGen {
@@ -134,7 +134,7 @@ func (f randTestingFramework) runRandTestRepeated(t *testing.T) {
 	}
 }
 
-// Helper Functo
+// Helper Function
 // loadClusterInfo creates a LoadedCluster from a matching ClusterInfo based on
 // the given configNam, or panics if no match is found in existing
 // configurations.

pkg/kv/kvserver/asim/tests/rand_gen.go

@@ -0,0 +1,25 @@
+// Copyright 2023 The Cockroach Authors.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+package tests
+
+import (
+	"math/rand"
+
+	"github.com/cockroachdb/cockroach/pkg/kv/kvserver/asim/gen"
+	"github.com/cockroachdb/cockroach/pkg/kv/kvserver/asim/state"
+)
+
+// randomClusterInfoGen randomly picks a predefined configuration.
+func (f randTestingFramework) randomClusterInfoGen(randSource *rand.Rand) gen.LoadedCluster {
+	chosenIndex := randSource.Intn(len(state.ClusterOptions))
+	chosenType := state.ClusterOptions[chosenIndex]
+	return loadClusterInfo(chosenType)
+}

pkg/kv/kvserver/asim/tests/rand_test.go

@@ -42,7 +42,7 @@ func defaultSettings(randOptions map[string]bool) testSettings {
 // for output + add more tests to cover cases that are not tested by default
 func TestRandomized(t *testing.T) {
 	randOptions := map[string]bool{
-		"cluster":         false,
+		"cluster":         true,
 		"ranges":          false,
 		"load":            false,
 		"static_settings": false,