Test case for backend is failing

[qriz1452]

Here is the console output for the failed testcase :

+ npm test

> server@1.0.0 test
> cross-env NODE_ENV=test jest --testTimeout=5000

FAIL tests/activity.test.js
  GET /api/activities
    ✕ should get all the activities (4 ms)

  ● GET /api/activities › should get all the activities

    MongooseError: The `uri` parameter to `openUri()` must be a string, got "undefined". Make sure the first parameter to `mongoose.connect()` or `mongoose.createConnection()` is a string.

       8 | /* Connecting to the database before each test. */
       9 | beforeEach(async () => {
    > 10 |   await mongoose.connect(process.env.MONGODB_URI);
         |                  ^
      11 | });
      12 |
      13 | /* Closing database connection after each test. */

      at NativeConnection.Object.<anonymous>.Connection.openUri (node_modules/mongoose/lib/connection.js:689:11)
      at node_modules/mongoose/lib/index.js:379:10
      at node_modules/mongoose/lib/helpers/promiseOrCallback.js:32:5
      at promiseOrCallback (node_modules/mongoose/lib/helpers/promiseOrCallback.js:31:10)
      at Mongoose.Object.<anonymous>.Mongoose._promiseOrCallback (node_modules/mongoose/lib/index.js:1224:10)
      at Mongoose.Object.<anonymous>.Mongoose.connect (node_modules/mongoose/lib/index.js:378:20)
      at Object.connect (tests/activity.test.js:10:18)

Test Suites: 1 failed, 1 total
Tests:       1 failed, 1 total
Snapshots:   0 total
Time:        1.492 s
Ran all test suites.