},
		{
			example: hex("3bffffffffffffffff"),
			reject:  "-2^64-1 overflows int64 and falling back to float64 (as with JSON) loses distinction between float and integer",
		},
		{
			example: hex("c349010000000000000000"),
			reject:  "-18446744073709551617 overflows int64 and falling back to float64 (as with JSON) loses distinction between float and integer",
			fixme:   "decoding negative bigint to interface{} must not produce math/big.Int",

					if e == nil {
						t.Error("expected non-nil error")
					}
				},
			},
		})

		group(t, "negative bignum", []test{
			{
				name:  "rejected",
				in:    hex("c349010000000000000000"), // 3(-18446744073709551617)
				fixme: "decoding cbor data tagged with 3 produces big.Int instead of rejecting",
				assertOnError: func(t *testing.T, e error) {
					// TODO: Once this can pass, make the assertion stronger.