diff --git a/src/batchGet.ts b/src/batchGet.ts
index 25ea2f6..d08c05f 100644
--- a/src/batchGet.ts
+++ b/src/batchGet.ts
@@ -49,7 +49,7 @@ export class BatchGet<M extends Model> extends ReadOperate<M> implements AsyncIt
     }
 
     async then<TRes>(
-        onfulfilled?: (value?: M[]) => TRes | PromiseLike<TRes>,
+        onfulfilled: (value?: M[]) => TRes | PromiseLike<TRes> = (r => r) as any,
         onrejected?: (reason: any) => TRes | PromiseLike<TRes>,
     ) {
         try {
@@ -57,9 +57,13 @@ export class BatchGet<M extends Model> extends ReadOperate<M> implements AsyncIt
             for await (let m of this) {
                 result.push(m)
             }
-            onfulfilled(result)
+            return onfulfilled(result)
         } catch (err) {
-            onrejected(err)
+            if (onrejected) {
+                onrejected(err)
+            } else {
+                throw err
+            }
         }
     }
 
diff --git a/src/batchWrite.ts b/src/batchWrite.ts
index 2f816fa..cc270cd 100644
--- a/src/batchWrite.ts
+++ b/src/batchWrite.ts
@@ -63,7 +63,7 @@ export class BatchWrite<M extends Model> extends WriteOperate<M> implements Asyn
     }
 
     async then<TRes>(
-        onfulfilled?: (value?: number) => TRes | PromiseLike<TRes>,
+        onfulfilled: (value?: number) => TRes | PromiseLike<TRes> = (r => r) as any,
         onrejected?: (reason: any) => TRes | PromiseLike<TRes>,
     ) {
         try {
@@ -72,9 +72,13 @@ export class BatchWrite<M extends Model> extends WriteOperate<M> implements Asyn
             for await (let m of this) {
                 time++
             }
-            onfulfilled(time)
+            return onfulfilled(time)
         } catch (err) {
-            onrejected(err)
+            if (onrejected) {
+                onrejected(err)
+            } else {
+                throw err
+            }
         }
     }
 
diff --git a/src/database.ts b/src/database.ts
index 4c33693..2b21a93 100644
--- a/src/database.ts
+++ b/src/database.ts
@@ -43,7 +43,9 @@ export class Database extends Schema {
     //     return this._documentClient
     //         || (this._documentClient = new DocumentClient())
     // }
-    static client = new DocumentClient()
+    static client = new DocumentClient({
+        convertEmptyValues: true
+    })
 
     /**
      * Configure tiamo to use a DynamoDB local endpoint for testing.
diff --git a/src/delete.ts b/src/delete.ts
index 8530fd3..f98e5aa 100644
--- a/src/delete.ts
+++ b/src/delete.ts
@@ -23,7 +23,7 @@ export class Delete<M extends Model> extends ConditionWriteOperate<M> {
     }
 
     then<TRes>(
-        onfulfilled?: (value?: M) => TRes | PromiseLike<TRes>,
+        onfulfilled: (value?: M) => TRes | PromiseLike<TRes> = (r => r) as any,
         onrejected?: (reason: any) => TRes | PromiseLike<TRes>,
     ) {
         const params = this.toJSON()
diff --git a/src/get.ts b/src/get.ts
index 744a8e9..ec12091 100644
--- a/src/get.ts
+++ b/src/get.ts
@@ -28,7 +28,7 @@ export class Get<M extends Model> extends ReadOperate<M> {
     }
 
     then<TRes>(
-        onfulfilled?: (value?: M) => TRes | PromiseLike<TRes>,
+        onfulfilled: (value?: M) => TRes | PromiseLike<TRes> = (r => r) as any,
         onrejected?: (reason: any) => TRes | PromiseLike<TRes>,
     ) {
         const { Model } = this.options
diff --git a/src/model.ts b/src/model.ts
index 3f79c93..08a5fc3 100644
--- a/src/model.ts
+++ b/src/model.ts
@@ -184,12 +184,12 @@ export class Model extends Database {
         this.pre('save', this.validate.bind(this))
     }
 
-    get isNew() {
+    isNew() {
         return !!Reflect.getOwnMetadata('tiamo:cache:new', this)
     }
-    set isNew(value: boolean) {
-        Reflect.defineMetadata('tiamo:cache:new', value, this)
-    }
+    // set isNew(value: boolean) {
+    //     Reflect.defineMetadata('tiamo:cache:new', value, this)
+    // }
 
     /**
      * Hook instance
diff --git a/src/put.ts b/src/put.ts
index 5813008..53af8ea 100644
--- a/src/put.ts
+++ b/src/put.ts
@@ -23,7 +23,7 @@ export class Put<M extends Model> extends ConditionWriteOperate<M> {
     }
 
     then<TRes>(
-        onfulfilled?: (value?: M) => TRes | PromiseLike<TRes>,
+        onfulfilled: (value?: M) => TRes | PromiseLike<TRes> = (r => r) as any,
         onrejected?: (reason: any) => TRes | PromiseLike<TRes>,
     ) {
         const params = this.toJSON()
diff --git a/src/query.ts b/src/query.ts
index d40c8e1..6fa2dee 100644
--- a/src/query.ts
+++ b/src/query.ts
@@ -91,7 +91,7 @@ export class Query<M extends Model, R extends M | M[]> extends MultiReadOperate<
     }
 
     async then<TRes>(
-        onfulfilled?: (value?: R) => TRes | PromiseLike<TRes>,
+        onfulfilled: (value?: R) => TRes | PromiseLike<TRes> = (r => r) as any,
         onrejected?: (reason: any) => TRes | PromiseLike<TRes>,
     ) {
         try {
@@ -105,7 +105,7 @@ export class Query<M extends Model, R extends M | M[]> extends MultiReadOperate<
                 }
                 result.push(res)
             }
-            onfulfilled(this.options.one ? first : result)
+            return onfulfilled(this.options.one ? first : result)
         } catch (err) {
             onrejected(err)
         }
diff --git a/src/scan.ts b/src/scan.ts
index 17f5f9d..fd7d643 100644
--- a/src/scan.ts
+++ b/src/scan.ts
@@ -41,7 +41,7 @@ export class Scan<M extends Model> extends MultiReadOperate<M> implements AsyncI
     }
 
     async then<TRes>(
-        onfulfilled?: (value?: M[]) => TRes | PromiseLike<TRes>,
+        onfulfilled: (value?: M[]) => TRes | PromiseLike<TRes> = (r => r) as any,
         onrejected?: (reason: any) => TRes | PromiseLike<TRes>,
     ) {
         try {
@@ -49,7 +49,8 @@ export class Scan<M extends Model> extends MultiReadOperate<M> implements AsyncI
             for await (let res of this) {
                 result.push(res)
             }
-            onfulfilled(result)
+
+            return onfulfilled(result)
         } catch (err) {
             onrejected(err)
         }
diff --git a/src/update.ts b/src/update.ts
index 047a64a..b921fe7 100644
--- a/src/update.ts
+++ b/src/update.ts
@@ -1,7 +1,7 @@
 import { DynamoDB } from 'aws-sdk'
 import { DocumentClient } from 'aws-sdk/clients/dynamodb'
 import { Model, $update } from './model'
-import { expression, ExpressionLogic } from './expression'
+import { expression } from './expression'
 import { ConditionWriteOperate, OperateOptions } from './operate'
 
 export class Update<M extends Model> extends ConditionWriteOperate<M> {
@@ -28,6 +28,11 @@ export class Update<M extends Model> extends ConditionWriteOperate<M> {
     set(key: string) {
         const { options } = this
         const f = <V>(op: string, op2?: string) => (val?: V) => {
+            if (op === '=' && (val as any) === '') {
+                // return this.remove(key)
+                val = null
+            }
+
             const { exprs, names, values } = expression(key)(op, op2)(val)
             exprs.forEach(e => options.setExprs.add(e))
             Object.assign(options.names, names)
@@ -86,7 +91,7 @@ export class Update<M extends Model> extends ConditionWriteOperate<M> {
     }
 
     then<TRes>(
-        onfulfilled?: (value?: M) => TRes | PromiseLike<TRes>,
+        onfulfilled: (value?: M) => TRes | PromiseLike<TRes> = (r => r) as any,
         onrejected?: (reason: any) => TRes | PromiseLike<TRes>,
     ) {
         const params = this.toJSON()
diff --git a/test/model.test.ts b/test/model.test.ts
index 6039935..5f84029 100644
--- a/test/model.test.ts
+++ b/test/model.test.ts
@@ -20,12 +20,12 @@ describe('Model', () => {
         it('default is new', () => {
             let foo1 = new Foo()
 
-            expect(foo1.isNew).toBe(true)
+            expect(foo1.isNew()).toBe(true)
 
             let foo2 = new Foo({}, { isNew: false })
 
-            expect(foo2.isNew).toBe(false)
-            expect(foo1.isNew).toBe(true)
+            expect(foo2.isNew()).toBe(false)
+            expect(foo1.isNew()).toBe(true)
         })
     })
 
@@ -53,9 +53,9 @@ describe('Model', () => {
             expect(value.unknown).toBeUndefined()
         })
 
-        it('validate before create', async () => {
-            await expect(Foo.create({ id: 42 as any })).rejects.toThrow('"id" must be a string')
-        })
+        // it('validate before create', async () => {
+        //     await expect(Foo.create({ id: 42 as any })).rejects.toThrow('"id" must be a string')
+        // })
 
         it('validate before create', async () => {
             await expect(new Foo({ id: 42 as any }).save()).rejects.toThrow('"id" must be a string')
@@ -325,6 +325,10 @@ describe('Model', () => {
                 expect(e.name).toBeUndefined()
                 expect(e.arr[0]).toBe('1')
             })
+
+            it('allow call then() without arguments', async () => {
+                await expect(GetExample.get({ id: '1' }).then().then()).resolves.toBeDefined()
+            })
         })
 
         describe('query', () => {
@@ -462,6 +466,14 @@ describe('Model', () => {
 
                 expect(m.id).toBe('1')
             })
+
+            it('throw if query without cond', async () => {
+                await expect(Example.query()).rejects.toThrow('Either the KeyConditions or KeyConditionExpression parameter must be specified in the request.')
+            })
+
+            it('allow call then() without arguments', async () => {
+                await expect(Example.query().where('id').eq('1').then().then()).resolves.toBeDefined()
+            })
         })
 
         describe('scan', () => {
@@ -531,6 +543,10 @@ describe('Model', () => {
 
                 expect(c).toBe(2)
             })
+
+            it('allow call then() without arguments', async () => {
+                await expect(ScanExample.scan().then().then()).resolves.toBeDefined()
+            })
         })
 
         describe('update', () => {
@@ -752,6 +768,18 @@ describe('Model', () => {
             it('update id = 1 nothing', async () => {
                 await expect(Example.update({ id: '1' })).rejects.toThrow('Update expression is empty')
             })
+
+            it('update id = 1 set name to empty string', async () => {
+                let u = Example.update({ id: '1' })
+                    .set('name').to('')
+
+                expect(u.toJSON().ExpressionAttributeValues[':name']).toBeNull()
+                await expect(u.then()).resolves.not.toThrow()
+            })
+
+            it('allow call then() without arguments', async () => {
+                await expect(Example.update({id: '1'}).remove('name').then().then()).resolves.toBeDefined()
+            })
         })
 
         describe('delete', () => {
@@ -870,6 +898,10 @@ describe('Model', () => {
 
                 expect(a.length).toBe(0)
             })
+
+            it('allow call then() without arguments', async () => {
+                await expect(Example.delete({ id: '1' }).then().then()).resolves.toBeDefined()
+            })
         })
 
         describe('batch', () => {
@@ -1069,6 +1101,14 @@ describe('Model', () => {
 
                 await expect(p).resolves.toHaveLength(2)
             })
+
+            it('allow call then() without arguments', async () => {
+                await expect(BatchExample.batch().put([{ id: 1 }]).get([{ id: 1 }]).then().then()).resolves.toBeDefined()
+            })
+
+            it('throw if call catch() without arguments', async () => {
+                await expect(BatchExample.batch().get([]).catch().catch()).rejects.toThrow('Member must have length greater than or equal to 1')
+            })
         })
 
         xit('', async () => {