Add isSubscriptionToken assertion

packages/contract-wrappers/src/contract_wrappers/erc20_token_wrapper.ts

@@ -379,6 +379,7 @@ export class ERC20TokenWrapper extends ContractWrapper {
      * @param   subscriptionToken Subscription token returned by `subscribe()`
      */
     public unsubscribe(subscriptionToken: string): void {
+        assert.isValidSubscriptionToken('subscriptionToken', subscriptionToken);
         this._unsubscribe(subscriptionToken);
     }
     /**

packages/contract-wrappers/src/contract_wrappers/erc721_token_wrapper.ts

@@ -411,6 +411,7 @@ export class ERC721TokenWrapper extends ContractWrapper {
      * @param   subscriptionToken Subscription token returned by `subscribe()`
      */
     public unsubscribe(subscriptionToken: string): void {
+        assert.isValidSubscriptionToken('subscriptionToken', subscriptionToken);
         this._unsubscribe(subscriptionToken);
     }
     /**

packages/contract-wrappers/src/contract_wrappers/ether_token_wrapper.ts

@@ -168,6 +168,7 @@ export class EtherTokenWrapper extends ContractWrapper {
      * @param   subscriptionToken Subscription token returned by `subscribe()`
      */
     public unsubscribe(subscriptionToken: string): void {
+        assert.isValidSubscriptionToken('subscriptionToken', subscriptionToken);
         this._unsubscribe(subscriptionToken);
     }
     /**

packages/contract-wrappers/src/utils/assert.ts

@@ -18,6 +18,11 @@ export const assert = {
         const isValid = await isValidSignatureAsync(provider, orderHash, signature, signerAddress);
         this.assert(isValid, `Expected order with hash '${orderHash}' to have a valid signature`);
     },
+    isValidSubscriptionToken(variableName: string, subscriptionToken: string): void {
+        const uuidRegex = new RegExp('^[a-fA-F0-9]{8}-[a-fA-F0-9]{4}-[a-fA-F0-9]{4}-[a-fA-F0-9]{4}-[a-fA-F0-9]{12}$');
+        const isValid = uuidRegex.test(subscriptionToken);
+        this.assert(isValid, `Expected ${variableName} to be a valid subscription token`);
+    },
     async isSenderAddressAsync(
         variableName: string,
         senderAddressHex: string,