Reactjs 凭证失败：第一个参数"；代币；必须是有效字符串或有效对象

为什么在尝试运行测试时出现以下错误：

在firebase中使用TODO进行测试

每个“hook for”之前的“×”应切换Todo和分派更新\u Todo 行动 Chrome 61.0.3163（Windows 10 0.0.0）

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每个“hook for”之后的“×”应切换Todo并发送更新\u Todo 行动 Chrome 61.0.3163（Windows 10 0.0.0）

  credential failed: First argument "token" must be a valid string or a valid object

  TypeError: Cannot read property 'remove' of undefined
      at Context.eval (eval at <anonymous> (app/tests/actions/actions.test.j

describe('Test with todos in firebase',() => {
    var testTodoRef;
    var uid;
    var todosRef;

    beforeEach((done) => {
      var credential = firebase.auth.GithubAuthProvider.credential(process.env.GITHUB_ACCESS_TOKEN);
      console.log('XXXX',credential);
      firebase.auth().signInWithCredential(credential).then((user) => {
        uid = user.uid;
        todosRef = firebaseRef.child(`users/${uid}/todos`);

        return todosRef.remove();
      }).then(() => {
        testTodoRef = todosRef.push();

        return testTodoRef.set({
          text: 'Something to do',
          completed: false,
          createdAt: 23453453
        })
      })
      .then(() => done())
      .catch(done);
    });

    afterEach((done) => {
      todosRef.remove().then(() => done());
    });