You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: shellout_unix_test.go
    path of file: ./repos/skeema/internal/shellout
    
    the code of the file until where you have to start completion: //go:build !windows
// +build !windo
    
func TestRunCapture(t *testing.T) {
	c := New("echo hello 1>&2; echo world")
	if output, err := c.RunCapture(); err != nil {
		t.Errorf("Unexpected error from RunCapture(): %v", err)
	} else if output != "world\n" {
		t.Errorf("Unexpected output from RunCapture(): %q", output)
	}

	// Test behavior when using WithStdin
	r := strings.NewReader("hello\nworld\nfoo\n\nbar\n")
	if out, err := New("wc -l").WithStdin(r).RunCapture(); err != nil {
		t.Errorf("Unexpected non-nil err: %v", err)
	} else if strings.TrimSpace(out) != "5" {
		t.Errorf("Expected output to be \"5\", instead found %q", strings.TrimSpace(out))
	}
}