chore: add unit testcases for files in Text format. #517

Job	Run time
e2e (v1.25.12, long-running-resume,from-volume-resume,median-stop)	14m 40s
e2e (v1.25.12, grid,bayesian-optimization,tpe,multivariate-tpe,cma-es,hyperband)	18m 11s
e2e (v1.25.12, file-metrics-collector,pytorchjob-mnist)	13m 11s
e2e (v1.25.12, median-stop-with-json-format,file-metrics-collector-with-json-format)	11m 27s
e2e (v1.26.6, long-running-resume,from-volume-resume,median-stop)	13m 49s
e2e (v1.26.6, grid,bayesian-optimization,tpe,multivariate-tpe,cma-es,hyperband)	18m 30s
e2e (v1.26.6, file-metrics-collector,pytorchjob-mnist)	11m 56s
e2e (v1.26.6, median-stop-with-json-format,file-metrics-collector-with-json-format)	12m 6s
e2e (v1.27.3, long-running-resume,from-volume-resume,median-stop)	15m 29s
e2e (v1.27.3, grid,bayesian-optimization,tpe,multivariate-tpe,cma-es,hyperband)	19m 26s
e2e (v1.27.3, file-metrics-collector,pytorchjob-mnist)	12m 37s
e2e (v1.27.3, median-stop-with-json-format,file-metrics-collector-with-json-format)	13m 7s
	2h 54m 29s

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