},
		{
			name:   "LargeWithinMiddle",
			base:   250,
			expect: 50,
			ranges: large,
		},
	}

	for _, test := range tests {
		t.Run(test.name, func(t *testing.T) {
			a := MakeAddrRanges(test.ranges...)
			i := a.FindSucc(test.base)
			if i != test.expect {
				t.Fatalf("expected %d, got %d", test.expect, i)
			}
		})
	}

// Add.
func NewAddrRanges() AddrRanges {
	r := addrRanges{}
	r.init(testSysStat)
	return AddrRanges{r, true}
}

// MakeAddrRanges creates a new addrRanges populated with
// the ranges in a.
//
// The returned AddrRanges is immutable, so methods like
// Add will fail.
func MakeAddrRanges(a ...AddrRange) AddrRanges {
	// Methods that manipulate the backing store of addrRanges.ranges should