Realizing that 100% coverage means nothing

Code coverage allows you to check what part of your library or application is actually run. Coverage measurement is generally used as a rough gauge of how thorough your test suites are. There are multiple types of code coverage for Ruby. Using the built-in coverage library, line coverage, branch coverage, and method coverage are all supported.

Line coverage is the simplest type of coverage. It allows you to check whether a line of code was ever executed during the testing process. This is important because any line without coverage during testing means the line was never tested at all. Now, just because the line was covered doesn't mean that the result of the line was actually tested. All it means is that at some point during testing, code somewhere on the line was executed.

Branch coverage takes the same idea as line coverage but takes it a step farther. It ensures that all branches in the code were taken. Suppose if you have the...