Yes, there are online mock tests available for the UPSC Mathematics Optional subject exam. These mock tests are designed to help candidates prepare for the exam by providing them with practice questions and a simulated test environment. Here are some key details about these online mock tests:

1. EduRev:
- EduRev is a popular online platform that offers a wide range of educational resources, including mock tests for various competitive exams, including the UPSC Mathematics Optional subject exam.
- They have a dedicated section for UPSC Mathematics Optional subject mock tests, which includes a collection of practice tests that cover the entire syllabus of the exam.
- These mock tests are designed by subject matter experts and are aimed at providing candidates with an accurate representation of the actual exam.
- The tests are available in an online format, allowing candidates to take them at their convenience from anywhere with an internet connection.

2. Features of EduRev Mock Tests:
- The mock tests on EduRev platform are designed to be user-friendly and provide an interactive learning experience.
- The tests include a variety of question types, including multiple-choice questions, numerical answer type questions, and descriptive questions.
- They provide detailed solutions and explanations for each question, allowing candidates to understand the concepts and techniques required to solve them.
- The tests also provide performance analysis and feedback, which helps candidates identify their strengths and weaknesses and focus on areas that need improvement.
- EduRev regularly updates and adds new mock tests to their collection, ensuring that candidates have access to the latest exam patterns and question types.

3. Benefits of Online Mock Tests:
- Online mock tests provide candidates with a realistic exam experience, helping them become familiar with the format, time constraints, and difficulty level of the actual exam.
- They help candidates assess their level of preparedness and identify areas that require more attention and practice.
- Mock tests also help candidates improve their time management skills, as they need to solve a large number of questions within a limited time frame.
- By practicing mock tests, candidates can gain confidence and reduce exam-related stress and anxiety.

4. How to Access EduRev Mock Tests:
- To access the mock tests for the UPSC Mathematics Optional subject exam on EduRev, candidates can visit the EduRev website or download the EduRev app from the Google Play Store.
- They can then create a free account or log in using their existing credentials.
- Once logged in, candidates can navigate to the UPSC Mathematics Optional subject section and access the available mock tests.

In conclusion, EduRev provides online mock tests for the UPSC Mathematics Optional subject exam, which are designed to help candidates prepare for the exam effectively. These mock tests offer a range of features and benefits, including a simulated test environment, detailed solutions, performance analysis, and the flexibility to practice at one's convenience.