The test runner progress bar turns red if any test fails.
This jargon phrase captures the three steps in an effective coding cycle: first describe an unmet need with a new test, prove that has been met without breaking anything else, then optimize the solution. post 
Test Driven Development is a significant culture change for many teams and throughput may initially drop as the practice beds in. Introducing TDD may be controversial in organizations with a separate QA testing function. However, productivity generally increases in line with improvements in code quality, and reduced rework can be expected. The practice also encourages a better understanding of requirements and their acceptance criteria. An automated test environment is recommended to gain the full benefits of TDD, since all tests should be run before any change is committed.