diff --git a/contracts/gwt.sol b/contracts/gwt.sol
index 943414f..dd68fe1 100644
--- a/contracts/gwt.sol
+++ b/contracts/gwt.sol
@@ -12,6 +12,8 @@ contract GWTToken is ERC20, Ownable {
     // 这种兑换币，是不是需要设定一个最大上限？
     constructor(address _dmcToken) ERC20("Gb storage per Week Token", "GWT") Ownable(msg.sender) {
         dmcToken = DMCToken(_dmcToken);
+        // enable mint and burn
+        allow_transfer[address(0)] = true;
     }
 
     function enableTransfer(address[] calldata addresses) public onlyOwner {
diff --git a/test/test_exchange.ts b/test/test_exchange.ts
new file mode 100644
index 0000000..22dcdcf
--- /dev/null
+++ b/test/test_exchange.ts
@@ -0,0 +1,64 @@
+import { ethers } from "hardhat"
+import { DMCToken, GWTToken } from "../typechain-types"
+import { HardhatEthersSigner } from '@nomicfoundation/hardhat-ethers/signers';
+import { expect } from "chai";
+
+describe("Exchange", function () {
+    let dmc: DMCToken
+    let gwt: GWTToken
+    let signers: HardhatEthersSigner[];
+
+    before(async () => {
+        signers = await ethers.getSigners()
+
+        dmc = await (await ethers.deployContract("DMCToken", [ethers.parseEther("10000000")])).waitForDeployment()
+        let dmcAddr = await dmc.getAddress();
+        gwt = await (await ethers.deployContract("GWTToken", [dmcAddr])).waitForDeployment()
+
+        await (await dmc.transfer(signers[1].address, ethers.parseEther("1000"))).wait()
+    })
+
+    it("exchange dmc to gwt", async () => {
+        expect(await dmc.balanceOf(signers[1].address)).to.equal(ethers.parseEther("1000"))
+        let gwtAddr = await gwt.getAddress();
+        await expect(dmc.connect(signers[1]).approve(gwtAddr, ethers.parseEther("1")))
+            .emit(dmc, "Approval").withArgs(signers[1].address, gwtAddr, ethers.parseEther("1"))
+
+        await expect(gwt.connect(signers[1]).exchange(ethers.parseEther("1")))
+            .emit(gwt, "Transfer").withArgs(ethers.ZeroAddress, signers[1].address, ethers.parseEther("210"))
+        
+        expect(await gwt.balanceOf(signers[1].address)).to.equal(ethers.parseEther("210"))
+        expect(await dmc.balanceOf(signers[1].address)).to.equal(ethers.parseEther("999"))
+        expect(await dmc.balanceOf(gwtAddr)).to.equal(ethers.parseEther("1"))
+    })
+
+    it("unregistered transfer will be reverted", async () => {
+        await expect(gwt.connect(signers[1]).transfer(signers[2].address, ethers.parseEther("1")))
+            .to.be.revertedWith("transfer not allowed")
+    })
+
+    it("register transfer", async () => {
+        // register signers[2]
+        await expect(gwt.connect(signers[0]).enableTransfer([signers[2].address])).to.be.ok;
+
+        // transfer to signers[2] success
+        await expect(gwt.connect(signers[1]).transfer(signers[2].address, ethers.parseEther("1")))
+            .emit(gwt, "Transfer").withArgs(signers[1].address, signers[2].address, ethers.parseEther("1"))
+
+        expect(await gwt.balanceOf(signers[2].address)).to.equal(ethers.parseEther("1"))
+
+        // transfer from signers[2] success
+        await expect(gwt.connect(signers[2]).transfer(signers[1].address, ethers.parseEther("1")))
+            .emit(gwt, "Transfer").withArgs(signers[2].address, signers[1].address, ethers.parseEther("1"))
+
+        expect(await gwt.balanceOf(signers[2].address)).to.equal(0)
+    })
+
+    it("burn", async () => {
+        await expect(gwt.connect(signers[1]).burn(ethers.parseEther("210")))
+            .emit(gwt, "Transfer").withArgs(signers[1].address, ethers.ZeroAddress, ethers.parseEther("210"))
+
+        expect(await gwt.balanceOf(signers[1].address)).to.equal(0)
+        expect(await dmc.balanceOf(signers[1].address)).to.equal(ethers.parseEther("1000"))
+    });
+})
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