[UnitTest] Add another unit tests to the data structures that contain the metadata.
[UnitTest] Add another unit tests to the data structures that contain the metadata.

I am adding this test mainly to check that the code that removed the sentinal
value and replaced it with a nullable pointer and some logic for initializing
the pointer works.

sschiau/swift,calebd/swift,benlangmuir/swift,xwu/swift,JaSpa/swift,apple/swift,natecook1000/swift,apple/swift,shahmishal/swift,shahmishal/swift,Jnosh/swift,karwa/swift,gregomni/swift,russbishop/swift,kstaring/swift,glessard/swift,kstaring/swift,tjw/swift,IngmarStein/swift,hooman/swift,CodaFi/swift,uasys/swift,tinysun212/swift-windows,frootloops/swift,tjw/swift,frootloops/swift,alblue/swift,devincoughlin/swift,jmgc/swift,brentdax/swift,devincoughlin/swift,djwbrown/swift,glessard/swift,brentdax/swift,tinysun212/swift-windows,uasys/swift,JaSpa/swift,devincoughlin/swift,frootloops/swift,SwiftAndroid/swift,shahmishal/swift,CodaFi/swift,therealbnut/swift,practicalswift/swift,hughbe/swift,amraboelela/swift,danielmartin/swift,lorentey/swift,austinzheng/swift,codestergit/swift,tjw/swift,gmilos/swift,codestergit/swift,tardieu/swift,ken0nek/swift,kstaring/swift,hughbe/swift,shajrawi/swift,swiftix/swift,swiftix/swift,tinysun212/swift-windows,KrishMunot/swift,kperryua/swift,glessard/swift,huonw/swift,sschiau/swift,manavgabhawala/swift,calebd/swift,austinzheng/swift,zisko/swift,practicalswift/swift,bitjammer/swift,rudkx/swift,return/swift,ken0nek/swift,airspeedswift/swift,tinysun212/swift-windows,dduan/swift,jmgc/swift,tjw/swift,xwu/swift,aschwaighofer/swift,practicalswift/swift,parkera/swift,SwiftAndroid/swift,austinzheng/swift,tinysun212/swift-windows,sschiau/swift,modocache/swift,stephentyrone/swift,hughbe/swift,sschiau/swift,practicalswift/swift,CodaFi/swift,jtbandes/swift,calebd/swift,ken0nek/swift,danielmartin/swift,JGiola/swift,benlangmuir/swift,nathawes/swift,brentdax/swift,Jnosh/swift,arvedviehweger/swift,zisko/swift,therealbnut/swift,brentdax/swift,huonw/swift,milseman/swift,jopamer/swift,djwbrown/swift,jckarter/swift,deyton/swift,codestergit/swift,aschwaighofer/swift,amraboelela/swift,therealbnut/swift,atrick/swift,rudkx/swift,gribozavr/swift,kperryua/swift,xedin/swift,alblue/swift,OscarSwanros/swift,airspeedswift/swift,harlanhaskins/swift,allevato/swift,return/swift,frootloops/swift,practicalswift/swift,danielmartin/swift,kperryua/swift,tkremenek/swift,CodaFi/swift,shahmishal/swift,roambotics/swift,Jnosh/swift,alblue/swift,rudkx/swift,ahoppen/swift,frootloops/swift,lorentey/swift,harlanhaskins/swift,modocache/swift,aschwaighofer/swift,danielmartin/swift,calebd/swift,gribozavr/swift,apple/swift,arvedviehweger/swift,swiftix/swift,arvedviehweger/swift,swiftix/swift,sschiau/swift,dduan/swift,shajrawi/swift,JGiola/swift,xedin/swift,gottesmm/swift,natecook1000/swift,natecook1000/swift,uasys/swift,ben-ng/swift,OscarSwanros/swift,djwbrown/swift,allevato/swift,hughbe/swift,jmgc/swift,benlangmuir/swift,return/swift,shajrawi/swift,roambotics/swift,felix91gr/swift,arvedviehweger/swift,kperryua/swift,ben-ng/swift,amraboelela/swift,tjw/swift,kstaring/swift,manavgabhawala/swift,gribozavr/swift,tinysun212/swift-windows,manavgabhawala/swift,alblue/swift,natecook1000/swift,ben-ng/swift,modocache/swift,return/swift,gottesmm/swift,KrishMunot/swift,gregomni/swift,calebd/swift,codestergit/swift,austinzheng/swift,roambotics/swift,aschwaighofer/swift,ken0nek/swift,milseman/swift,djwbrown/swift,zisko/swift,gottesmm/swift,practicalswift/swift,parkera/swift,calebd/swift,amraboelela/swift,alblue/swift,danielmartin/swift,milseman/swift,shahmishal/swift,atrick/swift,ken0nek/swift,gmilos/swift,huonw/swift,deyton/swift,roambotics/swift,jmgc/swift,lorentey/swift,bitjammer/swift,dduan/swift,amraboelela/swift,jckarter/swift,gottesmm/swift,aschwaighofer/swift,frootloops/swift,JGiola/swift,austinzheng/swift,kperryua/swift,allevato/swift,KrishMunot/swift,JGiola/swift,OscarSwanros/swift,ahoppen/swift,felix91gr/swift,tinysun212/swift-windows,gribozavr/swift,OscarSwanros/swift,harlanhaskins/swift,milseman/swift,xedin/swift,nathawes/swift,manavgabhawala/swift,SwiftAndroid/swift,jmgc/swift,Jnosh/swift,SwiftAndroid/swift,JGiola/swift,gregomni/swift,shajrawi/swift,felix91gr/swift,nathawes/swift,jckarter/swift,nathawes/swift,bitjammer/swift,CodaFi/swift,SwiftAndroid/swift,huonw/swift,shahmishal/swift,tardieu/swift,tkremenek/swift,OscarSwanros/swift,karwa/swift,stephentyrone/swift,gribozavr/swift,atrick/swift,manavgabhawala/swift,tjw/swift,stephentyrone/swift,therealbnut/swift,lorentey/swift,atrick/swift,amraboelela/swift,johnno1962d/swift,xwu/swift,airspeedswift/swift,jtbandes/swift,tjw/swift,djwbrown/swift,jtbandes/swift,johnno1962d/swift,OscarSwanros/swift,nathawes/swift,therealbnut/swift,nathawes/swift,gregomni/swift,austinzheng/swift,return/swift,russbishop/swift,zisko/swift,xwu/swift,bitjammer/swift,brentdax/swift,therealbnut/swift,karwa/swift,hooman/swift,SwiftAndroid/swift,lorentey/swift,karwa/swift,gottesmm/swift,codestergit/swift,ben-ng/swift,lorentey/swift,ahoppen/swift,arvedviehweger/swift,alblue/swift,KrishMunot/swift,hooman/swift,johnno1962d/swift,KrishMunot/swift,deyton/swift,tkremenek/swift,hughbe/swift,gottesmm/swift,SwiftAndroid/swift,milseman/swift,hooman/swift,kperryua/swift,kstaring/swift,Jnosh/swift,jmgc/swift,therealbnut/swift,danie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