Given you have a runningSum() function that sum ints from an array, testing a single case with a test func is simple to write and read.

With many contributors and many features, test suites are fate to grow.

Organization and readability might not follow though.

Many XCTests can have the same flow of data, while a few parameters change.

• Arrange an array, 

• arrange its expected output, 

• run function,

• assert output equals expectation.

Only the literal arrays change between these two test functions 

With SwiftTesting library, we 1. extract those parameters and 2. merge the two test cases into a single test function.

Now we can write only the test cases, instead of duplicating test functions !