This looks like a regression that is probably worth fixing in a 1.7.x. The testing package still says that it will run and verify example code, and only that the example may include the expected output.

Example functions without output comments are compiled but not executed.

@rakyl commented that they're not being compiled at all though, which is a regression

I cannot reproduce it. I am on 1.7 stable and I have just checked making one of examples, without an output section, invalid (s//fmt.Println/fmt.Printlnn and deleting the // Output: part) and the result is:

jnml@r550:~/src/github.com/cznic/gc$ head -n 15 ast_test.go 
// CAUTION: Generated by yy - DO NOT EDIT.

// Copyright 2016 The GC Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package gc

import (
    "fmt"
)

func ExampleArgument() {
    fmt.Printlnn(exampleAST(2, "package a ; 'b' ( 'c' )"))
}
jnml@r550:~/src/github.com/cznic/gc$ go test
# github.com/cznic/gc
./ast_test.go:14: undefined: fmt.Printlnn
FAIL    github.com/cznic/gc [build failed]
jnml@r550:~/src/github.com/cznic/gc$

I cannot produce this problem anymore. I was able to produce both against tip and go1.7. There was something sketchy about my env a week ago. I have little idea how it affected the example tests but am going to close this issue to avoid more noise.