Here are the Indian tests, but
miniaturisation is another important step altogether.. So if India was able to miniaturise its nuclear bombs to fit a missile warhead then it has the capability to launch nuclear tipped ballistic missiles..
1. Shakti I – A
thermonuclear device yielding 45 kt, but designed for up to 200 kt. (Powerfull to destroy the city like Mumbai).
2. Shakti II – A
plutonium implosion design yielding 15 kt and intended as a warhead that could be delivered by bomber or missile. It was an improvement of the device detonated in the 1974
Smiling Buddha (Pokhran-I) test of 1974, developed using simulations on the
PARAM supercomputer.
3. Shakti III – An experimental
boosted fission design that is used "non-
weapon grade"
[14] plutonium, but which likely omitted the material required for fusion, yielding 0.3 kt.
4. Shakti IV- A 0.5 kt experimental device.
5. Shakti V – A 0.2 kt experimental device that used
uranium-233.
The interesting part is all the tests have been carried out with super computers which have been built by ISRO and DRDO scientists. India had also developed the launching pads for the nuclear weapons in that time. This had helped to develop the missile program led by Dr. APJ Abdul Kalam.
https://www.quora.com/Why-were-nuclear-bombs-tested-by-India-twice-in-1974-and-1998
Number 1. test of a thermonuclear device was contested all over the world's scientific community, that leaves only number 2. as a potential threat but if based _as they say_ on the Smiling Buddha test, then it is still a primitive design!!!
Pokhran-II thermonuclear test, a failure
Several inaccuracies in the claims made by BARC and in the articles published in the press, including
The Hindu, on Pokhran-II need to be corrected. We have hard evidence on a purely factual basis, to inform the nation that not only was the yield of the second fusion (H-bomb) stage of the thermonuclear (TN) device tested in May 1998 was not only far below the design prediction made by the Bhabha Atomic Research Centre (BARC), but that it actually failed.
...
http://www.thehindu.com/opinion/op-ed/Pokhran-II-thermonuclear-test-a-failure/article13736892.ece