test: use modern Jest API instead of Jasmine

test/.eslintrc.yml

@@ -1,7 +1,6 @@
 
 env:
   jest: true
-  jasmine: true
 rules:
   no-require: off
   global-require: off

test/CSSTransition-test.js

@@ -3,14 +3,6 @@ import { mount } from 'enzyme';
 
 import CSSTransition from '../src/CSSTransition';
 
-jasmine.addMatchers({
-  toExist: () => ({
-    compare: actual => ({
-      pass: actual != null,
-    })
-  })
-});
-
 describe('CSSTransition', () => {
 
   it('should flush new props to the DOM before initiating a transition', (done) => {

test/CSSTransitionGroup-test.js

@@ -9,6 +9,7 @@ let TransitionGroup;
 // makes sure we're wired up correctly.
 describe('CSSTransitionGroup', () => {
   let container;
+  let consoleErrorSpy;
 
   function YoloTransition({ id, ...props }) {
     return (
@@ -28,7 +29,11 @@ describe('CSSTransitionGroup', () => {
     TransitionGroup = require('../src/TransitionGroup');
 
     container = document.createElement('div');
-    spyOn(console, 'error');
+    consoleErrorSpy = jest.spyOn(console, 'error').mockImplementation(() => {});
+  });
+
+  afterEach(() => {
+    consoleErrorSpy.mockRestore();
   });
 
 
@@ -55,7 +60,7 @@ describe('CSSTransitionGroup', () => {
     jest.runAllTimers();
 
     // No warnings
-    expect(console.error.calls.count()).toBe(0);
+    expect(consoleErrorSpy).not.toHaveBeenCalled();
 
     // The leaving child has been removed
     expect(ReactDOM.findDOMNode(a).childNodes.length).toBe(1);

test/Transition-test.js

@@ -11,12 +11,17 @@ import Transition, {
   EXITING,
 } from '../src/Transition'
 
-jasmine.addMatchers({
-  toExist: () => ({
-    compare: actual => ({
-      pass: actual != null,
-    }),
-  }),
+expect.extend({
+  toExist(received) {
+    const pass = received != null
+    return pass ? {
+      message: () => `expected ${received} to be null or undefined`,
+      pass: true,
+    } : {
+      message: () => `expected ${received} not to be null or undefined`,
+      pass: false,
+    }
+  },
 })
 
 describe('Transition', () => {