Test coverage with Claude Code: writing tests you'll actually trust

Getting Claude to write tests is easy. Getting Claude to write tests that actually catch bugs is harder. The problem with default test generation When you ask Claude to "add tests," it writes tests for the happy path. The function is called with valid input, the output is what the docstring says. This achieves coverage numbers but doesn't catch much. Tests get useful when they check: invalid input, boundary conditions, concurrent operations, error paths, and integration with other components.