Various fixes:
- Don't capitalize error messages
- Rename variables that collided with imports or types
- Prefer assert.Check over assert.Assert to prevent tests covering multiple
cases from failing early
- Fix inconsistent order of expected <--> actual, which made it difficult to
check which output was the expected output.
- Fix formatting of some comments
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>