go test -cpu=1 -run=X/Y -bench=X/Y -count=2 -v testregexp

# Test the following:

# TestX is run, twice
stdout -count=2 '^=== RUN   TestX$'
stdout -count=2 '^    x_test.go:6: LOG: X running$'

# TestX/Y is run, twice
stdout -count=2 '^=== RUN   TestX/Y$'
stdout -count=2 '^    x_test.go:8: LOG: Y running$'

# TestXX is run, twice
stdout -count=2 '^=== RUN   TestXX$'
stdout -count=2 '^    z_test.go:10: LOG: XX running'

# TestZ is not run
! stdout '^=== RUN   TestZ$'

# BenchmarkX is run with N=1 once, only to discover what sub-benchmarks it has,
# and should not print a final summary line.
stdout -count=1 '^    x_test.go:13: LOG: X running N=1$'
! stdout '^\s+BenchmarkX: x_test.go:13: LOG: X running N=\d\d+'
! stdout 'BenchmarkX\s+\d+'

# Same for BenchmarkXX.
stdout -count=1 '^    z_test.go:18: LOG: XX running N=1$'
! stdout  '^    z_test.go:18: LOG: XX running N=\d\d+'
! stdout 'BenchmarkXX\s+\d+'

# BenchmarkX/Y is run in full twice due to -count=2.
# "Run in full" means that it runs for approximately the default benchtime,
# but may cap out at N=1e9.
# We don't actually care what the final iteration count is, but it should be
# a large number, and the last iteration count prints right before the results.
stdout -count=2 '^    x_test.go:15: LOG: Y running N=[1-9]\d{4,}\nBenchmarkX/Y\s+\d+'

-- go.mod --
module testregexp

go 1.16
-- x_test.go --
package x

import "testing"

func TestX(t *testing.T) {
	t.Logf("LOG: X running")
	t.Run("Y", func(t *testing.T) {
		t.Logf("LOG: Y running")
	})
}

func BenchmarkX(b *testing.B) {
	b.Logf("LOG: X running N=%d", b.N)
	b.Run("Y", func(b *testing.B) {
		b.Logf("LOG: Y running N=%d", b.N)
	})
}
-- z_test.go --
package x

import "testing"

func TestZ(t *testing.T) {
	t.Logf("LOG: Z running")
}

func TestXX(t *testing.T) {
	t.Logf("LOG: XX running")
}

func BenchmarkZ(b *testing.B) {
	b.Logf("LOG: Z running N=%d", b.N)
}

func BenchmarkXX(b *testing.B) {
	b.Logf("LOG: XX running N=%d", b.N)
}