Make the coverage to 100%

[lichaozhy]

coverage snapshot on commit: 792b250

Coverage	∆	File	Lines	Relevant	Covered	Missed	Hits/Line	Branch Hits	Branch Misses
81.48		packages/jsonrpc/src/Client/index.js	79	37	31	6	50.0 + 17	13	4
83.33		packages/jsonrpc/src/Client/Batch.js	88	44	38	6	20.0 + 7	12	4
83.72		packages/jsonrpc/src/utils.js	90	39	33	6	36.0 + 12	39	8
86.67		packages/jsonrpc/src/Client/InvokingRegistry.js	49	23	22	1	26.0 + 9	4	3
87.5		packages/jsonrpc/src/Server/Caller.js	89	39	36	3	57.0 + 19	13	4
91.67		packages/jsonrpc/src/Server/normalize.js	64	25	23	2	93.0 + 31	21	2
94.59		packages/jsonrpc-duplex/src/normalize.js	92	40	37	3	54.0 + 18	33	1
95.0		packages/jsonrpc-duplex/index.js	71	18	17	1	35.0 + 12	2	0
98.15		packages/jsonrpc/src/Client/normalize.js	76	30	29	1	88.0 + 29	24	0