t.Errorf("pageCache flush did not clear cache")
		}

		// Set up the expected after state.
		afterAlloc := map[ChunkIdx][]BitRange{
			BaseChunkIdx: bits64ToBitRanges(^cache, base),
		}
		afterScav := map[ChunkIdx][]BitRange{
			BaseChunkIdx: bits64ToBitRanges(scav, base),
		}
		want := NewPageAlloc(afterAlloc, afterScav)
		defer FreePageAlloc(want)

		// Check to see if it worked.
		checkPageAlloc(t, want, b)