test: Some tests are missing in Symbolics.jl/src/utils.jl

[sivasathyaseeelan]

Issue Description:

Tests for some functions in Symbolics.jl/src/utils.jl are missing, which increases the risk of undetected issues in the codebase. This issue emphasizes the need to add comprehensive unit tests for the file.

Objective:

Improve the test coverage for Symbolics.jl/src/utils.jl by writing and integrating robust unit tests.

Details:

Develop tests to validate the functionality of the code.
Address edge cases and ensure appropriate error handling is tested.
Integrate the new tests into the existing test suite for seamless execution.

For reference, see the current file on Codecov.