added decho function for debugging output

if DEBUG is defined, then when decho is called, it will output the given
string to the console, prefixed with '# DEBUG: '

This allows easier debugging of tests but still will conditionally
output said output.

libexec/bats-exec-test

@@ -23,6 +23,13 @@ fi
 BATS_TEST_DIRNAME="$(dirname "$BATS_TEST_FILENAME")"
 BATS_TEST_NAMES=()
 
+# if DEBUG is set, write the given string to the console.
+decho() {
+  if [[ -n "$DEBUG" ]]; then
+    echo "# DEBUG: " $@ >&3
+  fi
+}
+
 load() {
   local filename="$BATS_TEST_DIRNAME/$1.bash"
   [ -f "$filename" ] || {

test/bats.bats

@@ -110,3 +110,16 @@ fixtures bats
   run bats "$FIXTURE_ROOT/dos_line.bats"
   [ $status -eq 0 ]
 }
+
+@test "test should not output DEBUG line if DEBUG is not set" {
+  run bats "$FIXTURE_ROOT/debug.bats"
+  [ $status -eq 0 ]
+  [[ ! $(echo $output | grep DEBUG) ]]
+}
+
+@test "test should output DEBUG line if DEBUG is set" {
+  export DEBUG=1
+  run bats "$FIXTURE_ROOT/debug.bats"
+  [ $status -eq 0 ]
+  echo $output | grep DEBUG
+}

test/fixtures/bats/debug.bats

@@ -0,0 +1,6 @@
+#!/usr/bin/env bats
+
+@test "this test contains decho call" {
+  decho "testing decho"
+  [[ 1 -eq 1 ]]
+}