1. Useful commands# 

$ go test -run "ExampleSession|TestSession" -v

Note that the -run flag is used for specifying test functions, not benchmarks, not fuzz test. Because example test is similar to test function, you can specify both example and test function with -run flag. If you want to specify benchmarks, use -bench flag:

-bench regexp
	Run benchmarks matching the regular expression.
-run regexp
	Run only tests and examples matching the regular expression.

# Flags below can be used with flags above.
-race
	enable data race detection.
-cover
	enable code coverage instrumentation.

Note that -bench does not disable the normal test selection. If you want run the benchmark test only you should pass -run=xxx to disable the normal test selection.

go test -run=xxx -bench 'BenchmarkDirectRead|BenchmarkLimitedRead'

# just one function, no single quote is fine: 
$ go test -run=xxx -bench BenchmarkStore

Learn more: go command - cmd/go - Go Packages

2. -bench & -benchmem#

The benchmark tool only reports heap allocations. Stack allocations via escape analysis are less costly, possibly free, so are not reported.

❯ go test -run=xxx -bench 'BenchmarkDirectRead|BenchmarkLimitedRead' -benchmem
BenchmarkDirectRead-8    38036484       31.47 ns/op      48 B/op      1 allocs/op
BenchmarkLimitedRead-8      12315       97480 ns/op      72 B/op      2 allocs/op

The -8 indicates that these benchmarks were run with a GOMAXPROCS value of 8, meaning up to 8 OS threads were used concurrently. This is typically set to the number of CPU cores available.

38036484`` for BenchmarkDirectRead and 12315`` for BenchmarkLimitedRead are the number of iterations the benchmark function was executed.

48 B/op: This means that on average, 48 bytes are being allocated per operation (op) in the benchmarked function.

Source: