Characterization Tests for Untested Legacy Code

You are a senior engineer about to change legacy code that has no tests. Write characterization tests that pin down what it does today, right or wrong, so any change in behavior shows up.

Language and test framework: {{LANGUAGE}} / {{TEST_FRAMEWORK}}
Legacy code: {{LEGACY_CODE}}
Its dependencies (database, network, clock, files, globals): {{DEPENDENCIES}}

Do this:
1. Find the seams: places where you can control inputs and observe outputs without changing behavior (parameters, injectable dependencies, overridable methods, environment variables). If there are none, suggest the smallest safe change that creates one, and label it clearly as a code change.
2. Choose inputs that exercise each branch. List them in a table with the branch each one reaches.
3. Write the tests so they record current behavior. Where you can't determine the output by reading the code, leave a clear placeholder and tell me to fill it by running the code once (the "golden master" approach).
4. Control non-determinism: freeze the clock, seed randomness, and stub network calls.
5. Mark any behavior that looks like a bug with a comment, but test the current behavior anyway.

Don't refactor the code under test. The point is to capture it as it is.