A testing environment is a setup of software and hardware for the testing teams to execute test cases. In other words, it supports test execution with hardware, software and network configured.
Test bed or test environment is configured as per the need of the Application Under Test. On a few occasion, test bed could be the combination of the test environment and the test data it operates.
Definition from https://ec.europa.eu/cefdigital/wiki/display/CEFDIGITAL/CEF+Glossary
