diff --git a/assembly/expect.ts b/assembly/expect.ts
index ac38205..fc1f326 100644
--- a/assembly/expect.ts
+++ b/assembly/expect.ts
@@ -2,11 +2,12 @@ import { equal, isNull } from "./comparison";
 import { assertResult } from "./env";
 import { toJson } from "./formatPrint";
 
-
+// @ts-ignore
 @inline
 const EXPECT_MAX_INDEX = 2147483647;
 
 export class Value<T> {
+  reversed: bool = false;
   data: T;
   constructor(_data: T) {
     this.data = _data;
@@ -110,4 +111,38 @@ export class Value<T> {
     }
     return this;
   }
+
+  isa<ExpectType>(codeInfoIndex: u32 = EXPECT_MAX_INDEX): Value<T> {
+    assertResult.collectCheckResult(
+      // @ts-ignore
+      this.data instanceof ExpectType,
+      codeInfoIndex,
+      // TODO: need extend chain information
+      `RTID<${load<u32>(changetype<usize>(this.data) - 8)}>`,
+      `RTID<${idof<ExpectType>()}>`,
+    );
+    return this;
+  }
+
+  isExactly<ExpectType>(codeInfoIndex: u32 = EXPECT_MAX_INDEX): Value<T> {
+    if (isNullable<T>()) {
+      if (this.data == null) {
+        assertResult.collectCheckResult(
+          false,
+          codeInfoIndex,
+          `<<null>>`,
+          `RTID<${idof<ExpectType>()}>`,
+        );
+        return this;
+      }
+    }
+    const rtid = load<u32>(changetype<usize>(this.data) - 8);
+    assertResult.collectCheckResult(
+      rtid == idof<ExpectType>(),
+      codeInfoIndex,
+      `RTID<${rtid}>`,
+      `RTID<${idof<ExpectType>()}>`,
+    );
+    return this;
+  }
 }
diff --git a/docs/api-documents/matchers.md b/docs/api-documents/matchers.md
index 4e6d895..212b064 100644
--- a/docs/api-documents/matchers.md
+++ b/docs/api-documents/matchers.md
@@ -26,5 +26,14 @@ Specially, for float type, use `closeTo` instead of `equal` to avoid rounding er
 
 ## Nullable
 
-`isNull` and `notNull` matcher can be used to a nullable object.
-Of cource, you can also use `equal` and `notEqual` to do same thing with explicit generic declartion `expect<T | null>()`
+`isNull` and `notNull` matchers can be used to a nullable object.
+Of course, you can also use `equal` and `notEqual` to do same thing with explicit generic declaration `expect<T | null>()`
+
+## Typing
+
+`isa` and `isExactly` matchers can be used to compare typing.
+
+In Assemblyscript, a variable has 2 kinds of types: the defined type and the runtime type. For example, when `Ext` extends `Base`, a variable declared as type `Base` may actually be of type `Ext` at runtime.
+
+- `isa` will check whether runtime type of given value is instance of expected type. In previous example, the runtime type of variable is instance of both `Base` and `Ext`.
+- `isExactly` will check whether runtime type of give value is exactly same as expected type. In previous example, the runtime type of variable is exactly `Ext` but not `Base`.
diff --git a/tests/as/expect.test.ts b/tests/as/expect.test.ts
index bcd375d..020fc4d 100644
--- a/tests/as/expect.test.ts
+++ b/tests/as/expect.test.ts
@@ -1,5 +1,11 @@
 import { describe, expect, test } from "../../assembly";
 
+class Base {}
+class Ext_0 extends Base {}
+class Ext_0_0 extends Ext_0 {}
+class Ext_1 extends Base {}
+class Ext_1_1 extends Ext_1 {}
+
 describe("expect", () => {
   test("< = >", () => {
     expect(1).greaterThan(0);
@@ -13,4 +19,11 @@ describe("expect", () => {
     expect<string | null>(null).isNull();
     expect<string | null>("test").notNull();
   });
+  test("isa", () => {
+    let ext: Base = new Ext_0_0();
+    expect(ext).isa<Base>();
+    expect(ext).isa<Ext_0>();
+    expect(ext).isa<Ext_0_0>();
+    expect(ext).isExactly<Ext_0_0>();
+  });
 });