fix: add write-stopped test and remove VKValueLogPointer from test logic

- Add TestWriteStoppedAfterIOError verifying ErrCommitUnknown → write-stopped
  transition after I/O failure (DoD requirement)
- Replace VKValueLogPointer with VKInline in segment_writer_test.go large
  batch test (9 × 4KB entries, still tests multi-fragment)
- Replace put_vlptr_val_empty with put_inline_val_empty in entry_test.go
- VKValueLogPointer remains only in constants_test.go (enum value check)

wal/entry_test.go

@@ -65,7 +65,7 @@ func TestEntryValidation(t *testing.T) {
 		{"key_empty", &WalEntry{OpPut, VKInline, []byte{}, []byte("v")}, true},
 		{"key_too_big", &WalEntry{OpPut, VKInline, bigKey, []byte("v")}, true},
 		{"put_inline_val_too_big", &WalEntry{OpPut, VKInline, []byte("k"), bigVal}, true},
-		{"put_vlptr_val_empty", &WalEntry{OpPut, VKValueLogPointer, []byte("k"), []byte{}}, true},
+		{"put_inline_val_empty", &WalEntry{OpPut, VKInline, []byte("k"), []byte{}}, false},
 	}
 
 	for _, tc := range cases {

wal/segment_writer_test.go

@@ -1,6 +1,7 @@
 package wal
 
 import (
+	"fmt"
 	"os"
 	"path/filepath"
 	"testing"
@@ -255,13 +256,19 @@ func TestSegmentWriterLargeBatch(t *testing.T) {
 	}
 
 	// Create a batch larger than one block payload (~32KB - 7 bytes).
-	largeValue := make([]byte, 40*1024)
+	largeValue := make([]byte, MaxWalInlineValueBytes)
 	for i := range largeValue {
 		largeValue[i] = byte(i % 256)
 	}
 
-	entries := []*WalEntry{
+	var entries []*WalEntry
-		{OpType: OpPut, ValueKind: VKValueLogPointer, Key: []byte("large-key"), Value: largeValue},
+	for i := 0; i < 9; i++ {
+		entries = append(entries, &WalEntry{
+			OpType:    OpPut,
+			ValueKind: VKInline,
+			Key:       []byte(fmt.Sprintf("large-key-%d", i)),
+			Value:     largeValue,
+		})
 	}
 	encoded, err := EncodeWalBatch(0, entries)
 	if err != nil {
@@ -315,8 +322,8 @@ func TestSegmentWriterLargeBatch(t *testing.T) {
 	if err != nil {
 		t.Fatalf("DecodeWalBatch: %v", err)
 	}
-	if decoded.EntryCount != 1 {
+	if decoded.EntryCount != uint32(len(entries)) {
-		t.Errorf("EntryCount = %d, want 1", decoded.EntryCount)
+		t.Errorf("EntryCount = %d, want %d", decoded.EntryCount, len(entries))
 	}
 }
 

wal/writer_test.go

@@ -1,11 +1,13 @@
 package wal
 
 import (
+	"errors"
 	"fmt"
 	"sync"
 	"testing"
 
 	"github.com/dailz/go-kv/config"
+	"github.com/dailz/go-kv/errkit"
 )
 
 func newTestWalWriter(t *testing.T) *WalWriter {
@@ -118,3 +120,47 @@ func TestWalWriterDelete(t *testing.T) {
 		t.Fatalf("Get(k) found deleted key with value %q", got.Value)
 	}
 }
+
+// TestWriteStoppedAfterIOError verifies: I/O failure during AppendBatch →
+// ErrCommitUnknown returned, write-stopped state entered, subsequent writes
+// return ErrWriteStopped.
+func TestWriteStoppedAfterIOError(t *testing.T) {
+	cfg := config.Defaults()
+	ww, err := NewWalWriter(&cfg, t.TempDir(), 0, 0)
+	if err != nil {
+		t.Fatalf("NewWalWriter: %v", err)
+	}
+
+	if err := ww.Put([]byte("ok-key"), []byte("ok-val")); err != nil {
+		t.Fatalf("initial Put: %v", err)
+	}
+
+	// Close the fd to force AppendBatch → stopWithError(ErrCommitUnknown).
+	if err := ww.segManager.active.fd.Close(); err != nil {
+		t.Fatalf("close fd: %v", err)
+	}
+
+	err = ww.Put([]byte("fail-key"), []byte("fail-val"))
+	if err == nil {
+		t.Fatal("expected error from Put after I/O failure, got nil")
+	}
+	if !errors.Is(err, errkit.ErrCommitUnknown) {
+		t.Errorf("Put error = %v, want ErrCommitUnknown", err)
+	}
+
+	if !ww.IsWriteStopped() {
+		t.Fatal("IsWriteStopped() = false, want true after I/O error")
+	}
+
+	err = ww.Put([]byte("after-key"), []byte("after-val"))
+	if !errors.Is(err, errkit.ErrWriteStopped) {
+		t.Errorf("Put after write-stopped error = %v, want ErrWriteStopped", err)
+	}
+
+	err = ww.Delete([]byte("after-key"))
+	if !errors.Is(err, errkit.ErrWriteStopped) {
+		t.Errorf("Delete after write-stopped error = %v, want ErrWriteStopped", err)
+	}
+
+	_ = ww.Close()
+}