nil *testing.T handling

[artem-nefedov]

Describe the bug

I've run into unclear behavior when *testing.T is nil, and I'm not sure if it's a bug or intended behavior.

I have a function that can be run from either tests or from a regular go program (in which case *testing.T doesn't exist), and that function contains shell.RunCommandAndGetOutput call. I realise this is probably a non-standard use of library, but still want to understand what's going on.

I found that this code will work fine:

	cmd := shell.Command{
		Command: "echo",
		Args: []string{"foo"},
		Logger: logger.Discard,
	}

	fmt.Println(shell.RunCommandAndGetOutput(nil, cmd))

But this code will crash will nil ptr dereference:

	cmd := shell.Command{
		Command: "echo",
		Args: []string{"foo"},
		Logger: logger.Discard,
	}

	var t *testing.T = nil
	fmt.Println(shell.RunCommandAndGetOutput(t, cmd))

Resulting in output:

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x2 addr=0x0 pc=0x100d81a60]

goroutine 1 [running]:
testing.(*T).Helper(0x1400000e168?)
        <autogenerated>:1 +0x20
github.com/gruntwork-io/terratest/modules/logger.(*Logger).Logf(0x100f83fc0, {0x100e8cfe8, 0x0}, {0x100df8c2b, 0x1f}, {0x1400006e260, 0x2, 0x2})
        /Users/user/go/pkg/mod/github.com/gruntwork-io/terratest@v0.45.0/modules/logger/logger.go:60 +0x54
github.com/gruntwork-io/terratest/modules/shell.runCommand({0x100e8cfe8, 0x0}, {{0x100df2237, 0x4}, {0x140000122b0, 0x1, 0x1}, {0x0, 0x0}, 0x0, ...})
        /Users/user/go/pkg/mod/github.com/gruntwork-io/terratest@v0.45.0/modules/shell/command.go:100 +0x104
github.com/gruntwork-io/terratest/modules/shell.RunCommandAndGetOutputE({0x100e8cfe8?, 0x0?}, {{0x100df2237, 0x4}, {0x140000122b0, 0x1, 0x1}, {0x0, 0x0}, 0x0, ...})
        /Users/user/go/pkg/mod/github.com/gruntwork-io/terratest@v0.45.0/modules/shell/command.go:58 +0x60
github.com/gruntwork-io/terratest/modules/shell.RunCommandAndGetOutput({0x100e8cfe8?, 0x0}, {{0x100df2237, 0x4}, {0x140000122b0, 0x1, 0x1}, {0x0, 0x0}, 0x0, ...})
        /Users/user/go/pkg/mod/github.com/gruntwork-io/terratest@v0.45.0/modules/shell/command.go:49 +0x64
main.main()
        /Users/user/a/main.go:18 +0xac
exit status 2

So, to work around this, I had to write this weird-looking construct:

if t == nil {
	out = shell.RunCommandAndGetOutput(nil, cmd)
} else {
	out = shell.RunCommandAndGetOutput(t, cmd)
}

Versions

• Terratest version: v0.45.0
• Environment details (Ubuntu 20.04, Windows 10, etc.): Mac/Linux

[denis256]

Hello,
since Terratest was intended to be used inside of Go tests, it is expected to have *testing.T passed in