add a test so that #2856 can be closed (#4102)

* add test for 2856

* rename variables

packages/react-navigation/src/views/__tests__/Transitioner-test.js

@@ -0,0 +1,49 @@
+/* eslint react/display-name:0 */
+import * as React from 'react';
+import renderer from 'react-test-renderer';
+import Transitioner from '../Transitioner';
+
+describe('Transitioner', () => {
+  it('should not trigger onTransitionStart and onTransitionEnd when route params are changed', () => {
+    const onTransitionStartCallback = jest.fn();
+    const onTransitionEndCallback = jest.fn();
+
+    const transitionerProps = {
+      configureTransition: (transitionProps, prevTransitionProps) => ({}),
+      navigation: {
+        state: {
+          index: 0,
+          routes: [
+            { key: '1', routeName: 'Foo' },
+            { key: '2', routeName: 'Bar' },
+          ],
+        },
+        goBack: () => false,
+        dispatch: () => false,
+        setParams: () => false,
+        navigate: () => false,
+      },
+      render: () => <div />,
+      onTransitionStart: onTransitionStartCallback,
+      onTransitionEnd: onTransitionEndCallback,
+    };
+
+    const nextTransitionerProps = {
+      ...transitionerProps,
+      navigation: {
+        ...transitionerProps.navigation,
+        state: {
+          index: 0,
+          routes: [
+            { key: '1', routeName: 'Foo', params: { name: 'Zoom' } },
+            { key: '2', routeName: 'Bar' },
+          ],
+        },
+      },
+    };
+    const component = renderer.create(<Transitioner {...transitionerProps} />);
+    component.update(<Transitioner {...nextTransitionerProps} />);
+    expect(onTransitionStartCallback).not.toBeCalled();
+    expect(onTransitionEndCallback).not.toBeCalled();
+  });
+});