Added BotState.delete() method and tests

libraries/botbuilder-core/src/botState.ts

@@ -151,6 +151,26 @@ export class BotState implements PropertyManager {
         return Promise.resolve();
     }
 
+    /**
+     * Delete the backing state object for the current turn.
+     *
+     * @remarks
+     * The state object will be removed from storage if it exists.  If the state object has been
+     * read in and cached, the cache will be cleared. 
+     *
+     * ```JavaScript
+     * await botState.delete(context);
+     * ```
+     * @param context Context for current turn of conversation with the user.
+     */
+    public delete(context: TurnContext): Promise<void> {
+        if (context.turnState.has(this.stateKey)) {
+            context.turnState.delete(this.stateKey);
+        }
+
+        return Promise.resolve(this.storageKey(context)).then((key: string) => this.storage.delete([key]));
+    }
+
     /**
      * Returns a cached state object or undefined if not cached.
      *

libraries/botbuilder-core/tests/botState.test.js

@@ -56,9 +56,20 @@ describe(`BotState`, function () {
         await botState.saveChanges(context);
 
         const items = await storage.read([storageKey]);
+        assert(items[storageKey], `state removed from storage.`);        
         assert(!items[storageKey].hasOwnProperty('test'), `state not cleared from storage.`);        
     });
 
+    it(`should delete() state storage.`, async function () {
+        await botState.load(context);
+        assert(cachedState(context, botState.stateKey), `invalid initial state`);
+        await botState.delete(context);
+        assert(!cachedState(context, botState.stateKey), `state not cleared on context.`);
+
+        const items = await storage.read([storageKey]);
+        assert(!items.hasOwnProperty(storageKey), `state not removed from storage.`);        
+    });
+
     it(`should force immediate saveChanges() of state to storage.`, function (done) {
         botState.load(context).then(() => {
             const state = cachedState(context, botState.stateKey);