AI coding: the test-first loop that makes review trivial
Ask the AI for failing tests first, approve them, then ask for the implementation. Review collapses to reading two diffs.
11 min · Reviewed 2026
The premise
Generating tests before implementation forces the AI to commit to a contract you can read in plain English. Once tests pass, the implementation is constrained and review becomes mechanical.
What AI does well here
Generate readable test cases from a behavior description
Iterate on implementation until provided tests pass
Surface ambiguities as test names you can question
What AI cannot do
Invent meaningful tests for behavior you never described
Catch missing test categories you didn't request
Decide whether the test list is complete enough to ship
End-of-lesson check
15 questions · take it digitally for instant feedback at tendril.neural-forge.io/learn/quiz/end-ai-coding-test-first-loop-r7a1-creators
Why does writing failing tests before requesting implementation make code review easier?
The AI skips writing documentation because tests are already complete
The AI will feel pressured to write perfect code on the first try
The failing tests automatically fix themselves once implementation begins
The tests create a readable contract that constrains what the implementation can do
What is the main risk of letting an AI write tests and implementation in the same conversation turn?
The code will run too slowly to test properly
The tests will use an incompatible programming language
The implementation will delete the test files by accident
The AI will shape both the tests and implementation to agree, potentially hiding bugs
In the test-first workflow, what should you ask the AI to do first when building a new feature?
Write the full implementation and then debug together
Write both tests and implementation simultaneously for speed
Generate failing tests covering the happy path, edge cases, and error conditions
Ask the AI to guess what kind of feature you might want
What capability of AI is most useful for generating tests from a behavior description?
AI can predict which features will be popular next year
AI can write code faster than humans can read it
AI can automatically deploy the code to production
AI can generate readable test cases that match the described behavior
A developer describes a feature and the AI generates tests with names like 'handles_empty_input' and 'rejects_negative_numbers'. What should the developer do next?
Discard the tests and write implementation directly
Ask the AI to combine the tests and implementation in one file
Approve these test names and then ask for the implementation
Have the AI generate more tests without reviewing the names
What can an AI reliably do in the test-first workflow?
Iterate on implementation until provided tests pass
Decide when the test suite is complete enough to ship
Determine which business requirements are most important
Invent meaningful tests for behavior the developer never described
What happens to code review in the test-first workflow once tests pass?
Review collapses to reading two simple diffs
Review takes longer because there are more files to check
Review becomes unnecessary because the AI is always correct
The AI skips review by automatically approving its own code
A student asks an AI to write tests for a 'sorting feature' but doesn't specify any specific behaviors. What limitation will the student likely encounter?
The AI cannot invent meaningful tests for behavior that wasn't described
The AI will refuse to write any tests
The AI will write tests for every possible sorting algorithm
The AI will ask the student for their credit card number
What does it mean to 'lock' the tests in the test-first workflow?
Archive the tests so they cannot be modified later
Put the test files in an encrypted folder
Finalize the test code before requesting implementation
Delete the implementation if tests fail three times
What is a 'contract' in the context of test-first AI coding?
A set of readable test cases that specify exactly what the implementation must do
A budget for how much the project will cost
A legal agreement between the developer and the AI company
A promise that the code will never have bugs
When should the human developer decide whether the test list is complete enough to ship?
After reviewing the generated test names for coverage
Never—the AI makes this decision
Before writing any tests
After the AI passes all the tests
What makes test-first review 'mechanical' rather than creative?
The tests are written in a secret code only AI understands
The implementation is already constrained to match the test contract
The AI refuses to allow any human input
Developers must solve complex logic puzzles
What type of output do tests provide that makes verification straightforward?
Verifiable outputs
Creative interpretations
Marketing claims
Ambiguous requirements
What is the relationship between test descriptions and implementation in the test-first workflow?
Tests are written after implementation to verify it works
Implementation is constrained to satisfy whatever the tests specify
Tests are optional and only used when bugs are suspected
Tests and implementation are written simultaneously by different AIs
Why is it important that test names be readable in plain English?
So humans can review and question the specification before implementation begins