beforeScav  map[ChunkIdx][]BitRange
		hits        []PageCache // expected base addresses and patterns
		afterAlloc  map[ChunkIdx][]BitRange
		afterScav   map[ChunkIdx][]BitRange
	}
	tests := map[string]test{
		"AllFree": {
			beforeAlloc: map[ChunkIdx][]BitRange{
				BaseChunkIdx: {},
			},
			beforeScav: map[ChunkIdx][]BitRange{
				BaseChunkIdx: {{1, 1}, {64, 64}},
			},
			hits: []PageCache{

		hits: []PallocSum{
			PackPallocSum(0, 5, 0),
		},
	}
	tests["One"] = test{
		free: []BitRange{{2, 1}},
		hits: []PallocSum{
			PackPallocSum(0, 1, 0),
		},
	}
	tests["AllFree"] = test{
		free: []BitRange{{0, PallocChunkPages}},
		hits: []PallocSum{
			emptySum,
		},
	}
	for name, v := range tests {
		v := v
		t.Run(name, func(t *testing.T) {
			b := makePallocBits(v.free)

			max:       PallocChunkPages,
			want:      BitRange{85, 1},
		},
	}
	// Try out different page minimums.
	for m := uintptr(1); m <= 64; m *= 2 {
		suffix := fmt.Sprintf("Min%d", m)
		tests["AllFree"+suffix] = test{
			min:  m,
			max:  PallocChunkPages,
			want: BitRange{0, PallocChunkPages},
		}
		tests["AllScavenged"+suffix] = test{
			scavenged: []BitRange{{0, PallocChunkPages}},
			min:       m,