That's an important indicator. You don't just build rockets and missiles and put them in storage. Periodic improvements and upgrades in already operating systems are almost a necessity, which would require flight testing for technological validations. If a new system is developed, it must be flight-tested. Unless you have outsourced everything to another country or are just buying off the shelf from them.
Nothing what you wrote is a contradiction to the information contained in this thread at all.
Many components and subsystems can be tested underground or in enclosed facilities such as static rocket motor tests, engine development, environmental testing, launch mechanism tests, guidance and electronics.
Which is why most countries with advanced missile programs often conduct more ground tests than flight tests.
Also there have been many reports (see this thread) that Saudi Arabian missiles are being tested by/in Pakistan and China because if KSA openly started firing missiles (for purposes of testing the missile trajectory, long-range flight stability, midcourse guidances and navigation over long distances, reentry vehicle performance at hypersonic speeds for instance, CEP, stage seperation under real flight conditions etc.), it would only get KSA sanctioned (likely) with a rabid Israel literally next door as well as US/European etc. opposition. Hardly needed when you can test well-known missile systems with partners abroad (if even needed). Especially if you now have (like KSA) local missile production and underground testing in the well over 50 + reported undreground missile bases.
I also suggest reading up on how the KSA-China missile deal in the 1980's and later cooperation even came to be. It was a completely covert operation to such an extent that the CIA itself only discovered it many years later when it was too late to prevent it.
Bruce Riedel (former CIA high-ranking official confirming what I am writing in this regard)
Lastly you really have to be either willfully ignorant or have a completely retarded leadership (which I doubt that the longest ruling dynasty in the region that controls the by far largest and richest country in the region no less, can be claimed to be), not to have established what Is being reported in the past 40 + years given regional developments, your almost unlimited money, resources, human capital, alliances. In fact I would claim that the leadership should commit collective seppuku if not the case which nothing points towards, luckily.