What is a 'test'? By definition, "a critical examination, observation or evaluation. A procedure intended to establish the quality, performance or reliability of something".
So this is why it's called a test - because it is.
And defined, for mine, by Sri Lanka's belligerent and determined batting on day four. I get why most New Zealand fans will be disappointed after yesterday's historic no-wicket-day at the Basin Reserve but, from a purist's perspective, it was exactly what the sport is about and also what it needs to keep this vital format alive and valid.
How easy would it have been for the Sri Lankans to throw their bats about, have a crack, score an acceptable 300 plus and surrender the two-game advantage?
No-one would've batted an eyelid in fact it was what most folk expected, almost assumed, would happen.
The closest comparison I can make between test cricket and other sports would be the seven-game series format used by the NBA, MLB and NHL. The point being that each individual game is only ever just that, another piece in the overall jigsaw whose picture only ever becomes completely clear when the final whistle is eventually blown.
For the first three days in Wellington the Black Caps were in complete control. Nothing from Sri Lanka indicated they'd be able to bat all day as a team let alone survive the day without losing a single wicket. They began the day 20-3, remember.
A very similar effort to what Kane Williamson and Henry Nicholls produced when hope was all but dead in that third and final test against Pakistan.
Impossible fightbacks, rearguard actions, and stonewall batting to simply save a test is what the sport is all about. It's as old as the game itself. Dragging a draw kicking and screaming from the jaws of defeat is a totally honourable result.
Case in point - the 1989 match in Perth when Mark Greatbatch singlehandedly defied the Australians for a day and a half to achieve a draw that is as prized as any of the precious eight victories we've ever had against them.
Cast your mind back to last summer and try and remember anything about any of the limited overs games or series or opponents we played in either Twenty20 or one-day formats.
Apart from Ross Taylor going berserk in Dunedin my mind is a complete blank - and I do this for a job!
But we all remember Ish Sodhi and Neil Wagner saving the second test and clinching that series win by holding out almost all of day five in Christchurch.
So celebrate what happened yesterday I say, because that display from Kusal Mendis and Angelo Mathews was exactly why test cricket is so special.
If you get it then no explanation is necessary, if you don't then there isn't one that will ever convince.