In general , what are the specifications of the input signal which will be sampled by ADC ?
How large is the input signal amplitude?
How large is the input signal frequency?
How large is the input signal power?
Your question is just to general..
If I say that most of ADC will have input range 0-5V it will be only partialy true.
Input signal max frequency? That depends on the sampling rate. Again, you can find ADCs which can comvert in ms, µs, ns...
Input signal power? I would use the word "negligible"..somewhere in µWs region..
You can talk only about particular ADC IC.
For example the AD676 ( https://www.analog.com/UploadedFiles/Data_Sheets/16663304ad676.pdf ).
Here you will need 3 supply voltages +5, +12 and -12, voltage refference (Vref) is between 5Vdc and 10Vdc and the Vin range is +/- Vref..
I think the testing depends on the resolution of the ADC you designed.
If the Spec is lower than some DAC in the market. you can buy one and design a test board by yourself. it is not necessary to have a high performance instrument.