env GO111MODULE=off

! go test x y
stdout ^FAIL\s+x
stdout ^ok\s+y
stdout (?-m)FAIL\n$

-- x/x_test.go --
package x

import "testing"

func TestNothingJustFail(t *testing.T) {
    t.Fail()
}

-- y/y_test.go --
package y