Tests

Most tests are "characterization" tests, meaning they represent the current output under these guidelines. This does not mean that it's the ideal output.
If you need to change an existing characterization, that's fine, so long as you're convinced it's no less correct than what was previously there.
See TestConstants for an automated way to rewrite the expected output en masse
Run hooks/enable-hooks.cmd to enable a pre-commit hook which stops you committing the flag when true

Types

Single file characterization tests (e.g. ExpressionTests.cs)
- When there are several test files that could accomodate a new test, pick the most specifically named one that covers what you're aiming to test.
Multi file characterization tests (e.g. MultiFileSolutionAndProjectTests.cs)
Single file self-verifying tests (e.g. EnumTests.vb)
- These are the only tests where the output is not in the repository.
- They convert a test method, and ensure it still passes.
- These can give great confidence that the conversion is correct.
- It's also possible for some conversion bugs to make the test pass for the wrong reason (in the extreme, imagine that the entire test method body became empty)

In general, the source and target of all test cases should compile.
- Exception: Things in the MissingSemanticModelInfo folder which specifically test common cases of incomplete input.
Some older tests have compile errors in the input or output. These will be gradually fixed over time.