Add small tests for prev context stack

Author: kitten

src/__tests__/suspense.test.js

@@ -338,19 +338,23 @@ describe('renderPrepass', () => {
       return null
     })
 
-    const Wrapper = () => (
-      <Fragment>
-        <Context.Provider value="a">
-          <TestA />
-        </Context.Provider>
-        <Context.Provider value="b">
-          <TestB />
-        </Context.Provider>
-        <Context.Provider value="c">
-          <TestC />
-        </Context.Provider>
-      </Fragment>
-    )
+    const Wrapper = () => {
+      expect(useContext(Context)).toBe('default')
+
+      return (
+        <Fragment>
+          <Context.Provider value="a">
+            <TestA />
+          </Context.Provider>
+          <Context.Provider value="b">
+            <TestB />
+          </Context.Provider>
+          <Context.Provider value="c">
+            <TestC />
+          </Context.Provider>
+        </Fragment>
+      )
+    }
 
     const render$ = renderPrepass(<Wrapper />)
     expect(TestC).toHaveBeenCalledTimes(1)

src/__tests__/visitor.test.js

@@ -13,6 +13,8 @@ import {
   setCurrentContextMap,
   getCurrentContextMap,
   getCurrentContextStore,
+  flushPrevContextMap,
+  flushPrevContextStore,
   readContextValue
 } from '../internals'
 
@@ -82,13 +84,15 @@ describe('visitElement', () => {
     }
 
     expect(readContextValue(Context)).toBe('testA')
+    expect(flushPrevContextStore()).toEqual([Context, undefined])
     expect(leaf).toHaveBeenCalledWith('testA')
 
     for (let i = 0, child = makeChild('testB'); i <= 3 && child; i++) {
       child = visitElement(child, [], () => {})[0]
     }
 
     expect(readContextValue(Context)).toBe('testB')
+    expect(flushPrevContextStore()).toEqual([Context, 'testA'])
     expect(leaf).toHaveBeenCalledWith('testB')
   })
 
@@ -227,8 +231,11 @@ describe('visitElement', () => {
 
     // We first populate the context
     visitElement(<Outer />, [], () => {})
+
     // Then manually mount Inner afterwards
     const children = visitElement(<Inner />, [], () => {})
+
+    expect(flushPrevContextMap()).toEqual({ value: undefined })
     expect(children.length).toBe(1)
     expect(children[0].type).toBe(Noop)
     expect(children[0].props.children).toBe('test')