diff --git a/libsql-sqlite3/src/test_walapi.c b/libsql-sqlite3/src/test_walapi.c
index 21a0bc5d4d..90d16cc9ff 100644
--- a/libsql-sqlite3/src/test_walapi.c
+++ b/libsql-sqlite3/src/test_walapi.c
@@ -1,8 +1,13 @@
 #include <sqlite3.h>
 #include <stdio.h>
+#include <stdlib.h>
+#include <stdint.h>
 #include <string.h>
 #include <assert.h>
 
+#define eprintf(...) fprintf(stderr, __VA_ARGS__)
+#define ensure(condition, ...) { if (!(condition)) { eprintf(__VA_ARGS__); exit(1); } }
+
 #if 0
 static void dump_frame(unsigned char *frame, size_t size){
   for(int addr=0; addr<size; addr+=16){
@@ -26,140 +31,100 @@ static void dump_frame(unsigned char *frame, size_t size){
 }
 #endif
 
-static int cmp_data(sqlite3 *db1, sqlite3 *db2){
+static void cmp_data(sqlite3 *db1, sqlite3 *db2){
   sqlite3_stmt *stmt1, *stmt2;
-  int rc;
-
-  rc = sqlite3_prepare_v2(db1, "SELECT HEX(x) FROM t", -1, &stmt1, 0);
-  if( rc!=SQLITE_OK ){
-    fprintf(stderr, "Can't prepare statement: %s\n", sqlite3_errmsg(db1));
-    return 1;
-  }
-
-  rc = sqlite3_prepare_v2(db2, "SELECT HEX(x) FROM t", -1, &stmt2, 0);
-  if( rc!=SQLITE_OK ){
-    fprintf(stderr, "Can't prepare statement: %s\n", sqlite3_errmsg(db2));
-    return 1;
-  }
+  ensure(sqlite3_prepare_v2(db1, "SELECT HEX(x) FROM t", -1, &stmt1, 0) == SQLITE_OK, "can't prepare statement: %s\n", sqlite3_errmsg(db1));
+  ensure(sqlite3_prepare_v2(db2, "SELECT HEX(x) FROM t", -1, &stmt2, 0) == SQLITE_OK, "can't prepare statement: %s\n", sqlite3_errmsg(db2));
 
   for(;;){
     int step1 = sqlite3_step(stmt1);
     int step2 = sqlite3_step(stmt2);
-    if( step1!=step2 ){
-      fprintf(stderr, "Step mismatch: %d != %d\n", step1, step2);
-      return 1;
-    }
+    ensure(step1 == step2, "step mismatch: %d != %d\n", step1, step2);
     if( step1!=SQLITE_ROW ){
       break;
     }
     const unsigned char *text1 = sqlite3_column_text(stmt1, 0);
     const unsigned char *text2 = sqlite3_column_text(stmt2, 0);
-    if( strncmp((const char *)text1, (const char *)text2, 4096)!=0 ){
-      fprintf(stderr, "Data mismatch\n");
-      return 1;
-    }
+    ensure(strncmp((const char *)text1, (const char *)text2, 4096) == 0, "data mismatch");
   }
-  return 0;
 }
 
-static int sync_db(sqlite3 *db_primary, sqlite3 *db_backup){
+static void sync_db(sqlite3 *db_primary, sqlite3 *db_backup){
   unsigned int max_frame;
-  int rc;
-
-  rc = libsql_wal_frame_count(db_primary, &max_frame);
-  if( rc!=SQLITE_OK ){
-    fprintf(stderr, "Can't get frame count: %s\n", sqlite3_errmsg(db_primary));
-    return 1;
-  }
-  rc = libsql_wal_insert_begin(db_backup);
-  if( rc!=SQLITE_OK ){
-    fprintf(stderr, "Can't begin commit: %s\n", sqlite3_errmsg(db_backup));
-    return 1;
-  }
+  ensure(libsql_wal_frame_count(db_primary, &max_frame) == SQLITE_OK, "can't get frame count: %s\n", sqlite3_errmsg(db_primary));
+  ensure(libsql_wal_insert_begin(db_backup) == SQLITE_OK, "can't begin commit: %s\n", sqlite3_errmsg(db_backup));
   for(int i=1; i<=max_frame; i++){
     char frame[4096+24];
-    rc = libsql_wal_get_frame(db_primary, i, frame, sizeof(frame));
-    if( rc!=SQLITE_OK ){
-      fprintf(stderr, "Can't get frame: %s\n", sqlite3_errmsg(db_primary));
-      return 1;
-    }
-    rc = libsql_wal_insert_frame(db_backup, i, frame, sizeof(frame));
-    if( rc!=SQLITE_OK ){
-      fprintf(stderr, "Can't inject frame %d: %s\n", rc, sqlite3_errmsg(db_backup));
-      return 1;
-    }
-  }
-  rc = libsql_wal_insert_end(db_backup);
-  if( rc!=SQLITE_OK ){
-    fprintf(stderr, "Can't end commit: %s\n", sqlite3_errmsg(db_backup));
-    return 1;
+    ensure(libsql_wal_get_frame(db_primary, i, frame, sizeof(frame)) == SQLITE_OK, "can't get frame: %s\n", sqlite3_errmsg(db_primary));
+    ensure(libsql_wal_insert_frame(db_backup, i, frame, sizeof(frame)) == SQLITE_OK, "can't inject frame: %s\n", sqlite3_errmsg(db_backup));
   }
-  return 0;
-}
-
-static void gen_data(sqlite3 *db){
-  sqlite3_exec(db, "CREATE TABLE t (x)", 0, 0, 0);
-  sqlite3_exec(db, "INSERT INTO t VALUES (randomblob(4 * 1024))", 0, 0, 0);
-  sqlite3_exec(db, "INSERT INTO t VALUES (randomblob(1 * 1024))", 0, 0, 0);
-  sqlite3_exec(db, "INSERT INTO t VALUES (randomblob(1 * 1024))", 0, 0, 0);
+  ensure(libsql_wal_insert_end(db_backup) == SQLITE_OK, "can't end commit: %s\n", sqlite3_errmsg(db_backup));
 }
 
-int open_db(const char *path, sqlite3 **db) {
-  int rc;
-
-  rc = sqlite3_open(path, db);
-  if (rc != SQLITE_OK) {
-    fprintf(stderr, "Can't open database %s: %s\n", path, sqlite3_errmsg(*db));
-    return rc;
-  }
-  rc = sqlite3_exec(*db, "PRAGMA journal_mode=WAL", NULL, NULL, NULL);
-  if (rc != SQLITE_OK) {
-    fprintf(stderr, "Can't set journal mode for %s: %s\n", path, sqlite3_errmsg(*db));
-    return rc;
-  }
-  rc = sqlite3_wal_autocheckpoint(*db, 0);
-  if (rc != SQLITE_OK) {
-      fprintf(stderr, "Can't disable checkpointing for %s: %s\n", path, sqlite3_errmsg(*db));
-      return rc;
-  }
-  return rc;
+void open_db(const char *path, sqlite3 **db) {
+  ensure(sqlite3_open(path, db) == SQLITE_OK, "can't open database %s: %s\n", path, sqlite3_errmsg(*db));
+  ensure(sqlite3_exec(*db, "PRAGMA journal_mode=WAL", NULL, NULL, NULL) == SQLITE_OK, "can't set journal mode for %s: %s\n", path, sqlite3_errmsg(*db));
+  ensure(sqlite3_wal_autocheckpoint(*db, 0) == SQLITE_OK, "can't disable checkpointing for %s: %s\n", path, sqlite3_errmsg(*db));
 }
 
-int main(int argc, char *argv[])
-{
+void test_huge_payload() {
     sqlite3 *db_primary, *db_backup;
     unsigned int max_frame;
-    int rc;
-
-    rc = open_db("primary.db", &db_primary);
-    if (rc != SQLITE_OK) {
-        return 1;
-    }
-    gen_data(db_primary);
-
-    rc = open_db("backup.db", &db_backup);
-    if (rc != SQLITE_OK) {
-        return 1;
-    }
-    rc = libsql_wal_frame_count(db_backup, &max_frame);
-    if (rc != SQLITE_OK) {
-        fprintf(stderr, "Can't get frame count for backup: %s\n", sqlite3_errmsg(db_backup));
-        return 1;
-    }
+    open_db("primary_test_huge_payload.db", &db_primary);
+    ensure(sqlite3_exec(db_primary, "CREATE TABLE t (x)", 0, 0, 0) == SQLITE_OK, "failed to insert data\n");
+    ensure(sqlite3_exec(db_primary, "INSERT INTO t VALUES (randomblob(4 * 1024))", 0, 0, 0) == SQLITE_OK, "failed to insert data\n");
+    ensure(sqlite3_exec(db_primary, "INSERT INTO t VALUES (randomblob(1 * 1024))", 0, 0, 0) == SQLITE_OK, "failed to insert data\n");
+    ensure(sqlite3_exec(db_primary, "INSERT INTO t VALUES (randomblob(1 * 1024))", 0, 0, 0) == SQLITE_OK, "failed to insert data\n");
+
+    open_db("backup_test_huge_payload.db", &db_backup);
+    ensure(libsql_wal_frame_count(db_backup, &max_frame) == SQLITE_OK, "failed to get frames count: %s\n", sqlite3_errmsg(db_backup));
     assert(max_frame == 0);
     
+    eprintf("start full sync\n");
     sync_db(db_primary, db_backup);
-
-    if (cmp_data(db_primary, db_backup)) {
-        return 1;
-    }
-
+    cmp_data(db_primary, db_backup);
     sync_db(db_primary, db_backup);
-    if (cmp_data(db_primary, db_backup)) {
-        return 1;
+    cmp_data(db_primary, db_backup);
+}
+
+void test_sync_by_parts() {
+    sqlite3 *db_primary, *db_backup;
+    unsigned int max_frame;
+    uint32_t in_commit = 0;
+    open_db("primary_test_sync_by_parts.db", &db_primary);
+    ensure(sqlite3_exec(db_primary, "CREATE TABLE t (x)", 0, 0, 0) == SQLITE_OK, "failed to insert data\n");
+    ensure(sqlite3_exec(db_primary, "INSERT INTO t VALUES (randomblob(4 * 1024))", 0, 0, 0) == SQLITE_OK, "failed to insert data\n");
+    ensure(sqlite3_exec(db_primary, "INSERT INTO t VALUES (randomblob(1 * 1024))", 0, 0, 0) == SQLITE_OK, "failed to insert data\n");
+    ensure(sqlite3_exec(db_primary, "INSERT INTO t VALUES (randomblob(1 * 1024))", 0, 0, 0) == SQLITE_OK, "failed to insert data\n");
+
+    open_db("backup_test_sync_by_parts.db", &db_backup);
+
+    ensure(libsql_wal_frame_count(db_primary, &max_frame) == SQLITE_OK, "can't get frame count: %s\n", sqlite3_errmsg(db_primary));
+    eprintf("start sync by parts\n");
+    for(int i=1; i<=max_frame; i++){
+      char frame[4096+24];
+      uint32_t is_commit;
+      ensure(libsql_wal_get_frame(db_primary, i, frame, sizeof(frame)) == SQLITE_OK, "can't get frame: %s\n", sqlite3_errmsg(db_primary));
+      is_commit = ((uint32_t)frame[4] << 24) + ((uint32_t)frame[5] << 16) + ((uint32_t)frame[6] << 8) + ((uint32_t)frame[7] << 0);
+      if (!in_commit) {
+        in_commit = 1;
+        ensure(libsql_wal_insert_begin(db_backup) == SQLITE_OK, "can't begin commit: %s\n", sqlite3_errmsg(db_backup));
+      }
+      ensure(libsql_wal_insert_frame(db_backup, i, frame, sizeof(frame)) == SQLITE_OK, "can't inject frame: %s\n", sqlite3_errmsg(db_backup));
+      if (is_commit) {
+        ensure(libsql_wal_insert_end(db_backup) == SQLITE_OK, "can't end commit: %s\n", sqlite3_errmsg(db_backup));
+        in_commit = 0;
+      }
     }
+    cmp_data(db_primary, db_backup);
+}
 
-    printf("OK\n");
+int main(int argc, char *argv[])
+{
+    test_huge_payload();
+    printf("============= OK test_huge_payload\n");
 
+    test_sync_by_parts();
+    printf("============= OK test_sync_by_parts\n");
     return 0;
 }