Add text endpoint integration tests

[StephenCathcart]

Description 🤔

The text endpoint is still under-tested and needs thorough integration tests.

Acceptance Criteria 🎉

• Ensure that all code conforms to our coding standards
• Written new unit / integration tests (or updated existing ones) for changes if necessary
• Verified that all unit / integration tests are passing
• Written doc blocks, inline documentation and updated READMEs on all new changes if necessary
• Both Travis CI and SonarCloud are passing

Please read CONTRIBUTING.md for details on our code of conduct.