While it is true that the USA can scrap the agreement and demand our returning their technology and fuel if we conduct tests for weapons in future, there are several inbuilt safeguards within the ambit of this agreement to prevent the Americans from dictating terms to us.
Before starting a "punitive" process, the USA will have to go through several rounds of discussions, compensate us according to prevailing international prices in such an unlikely event and cannot stop arbitrarily the supplies so as to bring our nuclear power stations to a grinding halt.
Therefore, even if we decide to go against the agreement and test for nuclear ordnance, the nation will be talking from a position of strength.