you could try paper trading on moneycontrol and stuff, using node. you could write your logic in js and test it.
Hi Fyers Team, Is there any option to test our logic/code before applying stratagies to the live market?
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What i did was to execute the code in an account with 0 balance and used debugger to provide expected values to emulate success from a failed response. Another option is to create expected responses and feed it to the application after you get a failure (It is expected since you are trying on an account with no balance) from the API. Once your code is ready check with stocks like ITC, which won't cost you much, but reliable ones.
Addition: You could also try applications like postman, where you could create a mock server with sample request and response of production API. Once the mock server is setup, you can hit it and receive response just like the API.