Content values are assigned null even after putting values in it

Question

As a part of Unit testing I wanted to insert values to DB using content resolver. But when I tried this,

 @Before
    public void runBeforeTestSignOut() {
        ContentValues values = new ContentValues();
        String userId="123";
        String userInfo="test";
        values.put(UserProvider.USER_ID, userId);
        values.put(UserProvider.USER_INFO, userInfo);
        System.out.print("Values are "+values);
        Uri uri = contentResolver.insert(UserProvider.CONTENT_USER_URI, values);
    }

Values are still assigned null. I can’t figure out why this is happening. I found some related questions but couldn’t find a solution. Please help me with this.