[GSoC] Add unit tests for `tune` API #1130

Job	Run time
e2e (v1.27.11, long-running-resume,from-volume-resume,median-stop)	15m 48s
e2e (v1.27.11, grid,bayesian-optimization,tpe,multivariate-tpe,cma-es,hyperband)	18m 5s
e2e (v1.27.11, file-metrics-collector,pytorchjob-mnist)	15m 31s
e2e (v1.27.11, median-stop-with-json-format,file-metrics-collector-with-json-format)	12m 14s
e2e (v1.28.7, long-running-resume,from-volume-resume,median-stop)	14m 48s
e2e (v1.28.7, grid,bayesian-optimization,tpe,multivariate-tpe,cma-es,hyperband)	20m 25s
e2e (v1.28.7, file-metrics-collector,pytorchjob-mnist)	12m 11s
e2e (v1.28.7, median-stop-with-json-format,file-metrics-collector-with-json-format)	13m 41s
e2e (v1.29.2, long-running-resume,from-volume-resume,median-stop)	16m 40s
e2e (v1.29.2, grid,bayesian-optimization,tpe,multivariate-tpe,cma-es,hyperband)	20m 33s
e2e (v1.29.2, file-metrics-collector,pytorchjob-mnist)	13m 16s
e2e (v1.29.2, median-stop-with-json-format,file-metrics-collector-with-json-format)	13m 0s
	3h 6m 12s

Provide feedback