Write 1 file. Write all code, no placeholders. Create the file at the EXACT path shown below (relative to the current working directory).

1. tests/test_calculator.py — Tests for a calculator module. Inline a `divide(a, b)` function that divides two numbers and raises ZeroDivisionError for zero denominators. Also inline a `save_result(path, value)` function that writes a float to a file. Write tests that cover: multiple input combinations for divide (positive, zero numerator, negative, fractional results) — use table-driven testing to avoid repetitive test functions. Test the zero-denominator error case and verify the error message text. Test save_result using a temporary directory provided by the test framework.
