diff --git a/params/config.libevm_test.go b/params/config.libevm_test.go
index 4f78888db3..cdbdf3cce6 100644
--- a/params/config.libevm_test.go
+++ b/params/config.libevm_test.go
@@ -2,8 +2,6 @@ package params
 
 import (
 	"encoding/json"
-	"fmt"
-	"log"
 	"math/big"
 	"testing"
 
@@ -16,88 +14,6 @@ func testOnlyClearRegisteredExtras() {
 	registeredExtras = nil
 }
 
-func ExampleRegisterExtras() {
-	type (
-		chainConfigExtra struct {
-			Foo string `json:"foo"`
-		}
-		rulesExtra struct {
-			FooCopy string
-		}
-	)
-
-	// In practice, this would be called inside an init() func and the `getter`
-	// used to access the ExtraPayload() values in a type-safe way.
-	getter := RegisterExtras(Extras[chainConfigExtra, rulesExtra]{
-		NewForRules: func(cc *ChainConfig, r *Rules, cEx *chainConfigExtra, blockNum *big.Int, isMerge bool, timestamp uint64) *rulesExtra {
-			// This function is called at the end of ChainConfig.Rules(),
-			// receiving a pointer to the Rules that will be returned. It MAY
-			// modify the Rules but MUST NOT modify the ChainConfig. The value
-			// that it returns will be available via Rules.ExtraPayload().
-			return &rulesExtra{
-				FooCopy: fmt.Sprintf("copy of: %q", cEx.Foo),
-			}
-		},
-	})
-	defer testOnlyClearRegisteredExtras()
-
-	// ChainConfig now unmarshals any JSON field named "extra" into a pointer to
-	// the registered type, which is available via the ExtraPayload() method.
-	buf := []byte(`{
-		"chainId": 1234,
-		"extra": {
-			"foo": "hello, world"
-		}
-	}`)
-
-	config := new(ChainConfig)
-	if err := json.Unmarshal(buf, config); err != nil {
-		log.Fatal(err)
-	}
-
-	fmt.Println(config.ChainID)
-	// The values returned by ExtraPayload() are guaranteed to be pointers to
-	// the registered types. They MAY, however, be nil pointers. In practice,
-	// callers SHOULD abstract the type assertion in a reusable function to
-	// provide a seamless devex.
-	ccExtra := getter.FromChainConfig(config)
-	rules := config.Rules(nil, false, 0)
-	rExtra := getter.FromRules(&rules)
-
-	if ccExtra != nil {
-		fmt.Println(ccExtra.Foo)
-	}
-	if rExtra != nil {
-		fmt.Println(rExtra.FooCopy)
-	}
-
-	// Output:
-	// 1234
-	// hello, world
-	// copy of: "hello, world"
-}
-
-func ExampleChainConfig_ExtraPayload() {
-	type (
-		chainConfigExtra struct{}
-		rulesExtra       struct{}
-	)
-	// Typically called in an `init()` function.
-	getter := RegisterExtras(Extras[chainConfigExtra, rulesExtra]{ /*...*/ })
-	defer testOnlyClearRegisteredExtras()
-
-	var c ChainConfig // Sourced from elsewhere, typically unmarshalled from JSON.
-
-	// Both ChainConfig.ExtraPayload() and Rules.ExtraPayload() return `any`
-	// that are guaranteed to be pointers to the registered types.
-	extra := getter.FromChainConfig(&c)
-
-	// Act on the extra payload...
-	if extra != nil {
-		// ...
-	}
-}
-
 type rawJSON struct {
 	json.RawMessage
 }
@@ -171,6 +87,7 @@ func TestRegisterExtras(t *testing.T) {
 
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
+			testOnlyClearRegisteredExtras()
 			tt.register()
 			defer testOnlyClearRegisteredExtras()
 
@@ -196,6 +113,9 @@ func TestRegisterExtras(t *testing.T) {
 }
 
 func TestExtrasPanic(t *testing.T) {
+	testOnlyClearRegisteredExtras()
+	defer testOnlyClearRegisteredExtras()
+
 	assertPanics(
 		t, func() {
 			RegisterExtras(Extras[int, struct{}]{})
@@ -225,7 +145,6 @@ func TestExtrasPanic(t *testing.T) {
 	)
 
 	RegisterExtras(Extras[struct{}, struct{}]{})
-	defer testOnlyClearRegisteredExtras()
 
 	assertPanics(
 		t, func() {
diff --git a/params/example.libevm_test.go b/params/example.libevm_test.go
index 0ca03cd3b6..16a88b3708 100644
--- a/params/example.libevm_test.go
+++ b/params/example.libevm_test.go
@@ -1,32 +1,22 @@
-package extraparams
+package params_test
 
 import (
+	"encoding/json"
+	"fmt"
+	"log"
 	"math/big"
 
 	"github.com/ethereum/go-ethereum/params"
 )
 
-var getter params.ExtraPayloadGetter[ChainConfigExtra, RulesExtra]
-
-func init() {
+// TODO: explain why this isn't in an init()
+func initFn() {
 	getter = params.RegisterExtras(params.Extras[ChainConfigExtra, RulesExtra]{
 		NewForRules: constructRulesExtra,
 	})
 }
 
-type ChainConfigExtra struct {
-	MyFeatureTime *uint64
-}
-
-type RulesExtra struct {
-	IsMyFeature bool
-}
-
-func constructRulesExtra(c *params.ChainConfig, r *params.Rules, cEx *ChainConfigExtra, blockNum *big.Int, isMerge bool, timestamp uint64) *RulesExtra {
-	return &RulesExtra{
-		IsMyFeature: isMerge && cEx.MyFeatureTime != nil && *cEx.MyFeatureTime < timestamp,
-	}
-}
+var getter params.ExtraPayloadGetter[ChainConfigExtra, RulesExtra]
 
 func FromChainConfig(c *params.ChainConfig) *ChainConfigExtra {
 	return getter.FromChainConfig(c)
@@ -35,3 +25,58 @@ func FromChainConfig(c *params.ChainConfig) *ChainConfigExtra {
 func FromRules(r *params.Rules) *RulesExtra {
 	return getter.FromRules(r)
 }
+
+type ChainConfigExtra struct {
+	MyForkTime *uint64 `json:"myForkTime"`
+}
+
+type RulesExtra struct {
+	IsMyFork bool
+}
+
+func constructRulesExtra(c *params.ChainConfig, r *params.Rules, cEx *ChainConfigExtra, blockNum *big.Int, isMerge bool, timestamp uint64) *RulesExtra {
+	return &RulesExtra{
+		IsMyFork: cEx.MyForkTime != nil && *cEx.MyForkTime <= timestamp,
+	}
+}
+
+func ExampleRegisterExtras() {
+	initFn() // TODO: explain
+
+	const forkTime = 530003640
+	jsonData := fmt.Sprintf(`{
+		"chainId": 1234,
+		"extra": {
+			"myForkTime": %d
+		}
+	}`, forkTime)
+
+	// ChainConfig now unmarshals any JSON field named "extra" into a pointer to
+	// the registered type, which is available via the ExtraPayload() method.
+	config := new(params.ChainConfig)
+	if err := json.Unmarshal([]byte(jsonData), config); err != nil {
+		log.Fatal(err)
+	}
+
+	fmt.Println(config.ChainID) // original geth fields work as expected
+
+	ccExtra := FromChainConfig(config)
+	if ccExtra != nil && ccExtra.MyForkTime != nil {
+		fmt.Println(*ccExtra.MyForkTime)
+	}
+
+	for _, time := range []uint64{forkTime - 1, forkTime, forkTime + 1} {
+		rules := config.Rules(nil, false, time)
+		rExtra := FromRules(&rules)
+		if rExtra != nil {
+			fmt.Printf("%+v\n", rExtra)
+		}
+	}
+
+	// Output:
+	// 1234
+	// 530003640
+	// &{IsMyFork:false}
+	// &{IsMyFork:true}
+	// &{IsMyFork:true}
+}