install: Pass global-module check in the absence of npm

test/install_script/nvm_check_global_modules

@@ -4,14 +4,19 @@ cleanup () {
   rm -rf "$npm_config_prefix/lib" >/dev/null 2>&1
   unset npm_config_prefix
 
+  rm -f npm
+  PATH="$ORIGINAL_PATH"
+
   unset -f setup cleanup die skip
-  unset message
+  unset message ORIGINAL_PATH
 }
 die () { echo $@ ; cleanup ; exit 1; }
 
 NVM_ENV=testing . ../../install.sh
 
 setup () {
+  ORIGINAL_PATH="$PATH"
+
   npm_config_prefix="$(pwd)"
   export npm_config_prefix
   mkdir -p "$npm_config_prefix/lib"
@@ -37,4 +42,13 @@ JSON
 message=$(nvm_check_global_modules)
 [ -z "$message" ] || die "nvm_check_global_modules should have not printed a notice when npm had only itself installed as a global module"
 
+# Faking the absence of npm
+PATH=".:$PATH"
+touch npm
+chmod +x npm
+
+message=$(nvm_check_global_modules)
+[ -z "$message" ] || die "nvm_check_global_modules should have not printed a notice when npm was unavailable"
+
+
 cleanup