Add the afterEach hook

Author: kasperpeulen

src/story.test.ts

@@ -39,6 +39,8 @@ async function doSomething() {
   a = 2;
 }
 
+async function validateSomething() {}
+
 async function cleanup() {
   a = 1;
 }
@@ -55,6 +57,9 @@ const simple: XMeta = {
     await doSomething();
     return cleanup;
   },
+  async afterEach() {
+    await validateSomething();
+  },
   args: { x: '1' },
   argTypes: { x: { type: { name: 'string' } } },
 };
@@ -71,6 +76,9 @@ const strict: XMeta<ButtonArgs> = {
     await doSomething();
     return cleanup;
   },
+  async afterEach() {
+    await validateSomething();
+  },
   argTypes: { x: { type: { name: 'string' } } },
 };
 

src/story.ts

@@ -261,6 +261,10 @@ export type BeforeEach<TRenderer extends Renderer = Renderer, TArgs = Args> = (
   context: StoryContext<TRenderer, TArgs>
 ) => Awaitable<CleanupCallback | void>;
 
+export type AfterEach<TRenderer extends Renderer = Renderer, TArgs = Args> = (
+  context: StoryContext<TRenderer, TArgs>
+) => Awaitable<void>;
+
 export interface Canvas {}
 
 export interface StoryContext<TRenderer extends Renderer = Renderer, TArgs = Args>
@@ -379,6 +383,17 @@ export interface BaseAnnotations<TRenderer extends Renderer = Renderer, TArgs =
    */
   beforeEach?: BeforeEach<TRenderer, TArgs>[] | BeforeEach<TRenderer, TArgs>;
 
+  /**
+   * Function to be called after each play function for post-test assertions.
+   * Don't use this function for cleaning up state.
+   * You can use the return callback of `beforeEach` for that, which is run when switching stories.
+   * When the function is async, it will be awaited.
+   *
+   * `afterEach` can be added to preview, the default export and to a specific story.
+   * They are run (and awaited) reverse order: preview, default export, story
+   */
+  afterEach?: AfterEach<TRenderer, TArgs>[] | BeforeEach<TRenderer, TArgs>;
+
   /**
    * Define a custom render function for the story(ies). If not passed, a default render function by the renderer will be used.
    */