Roman Numerals: Add Test Cases

Write more tests

It’s time to add more tests to our test suite to check if our DecimalToRoman function is behaving as expected.

Positive test cases

When testing our programs, we can’t rely exclusively on trivial input values. We also have to write tests for edge-corner cases, which are likely to uncover bugs and glitches in our production code. That said, let’s write tests for these values: 9, 45, 99, 222, 1024, and 3999.