tests: Provide an independent, auto-cleaned working directory to each test.

Fixes zsh-users/zsh-syntax-highlighting#182.
Prerequisite for testing issue #228.

* tests/test-highlighting.zsh
  (run_test): Move functionality to run_test_internal; make run_test be a wrapper
    that handles creating and cleaning up the tempdir.

* tests/README.md: Document the new feature.

* "highlighters/main/test-data/path-space- .zsh"
* highlighters/main/test-data/path-tilde-named.zsh
* highlighters/main/test-data/path.zsh
    Change test data to not depend on being run from the source directory.

highlighters/main/test-data/path-space- .zsh

@@ -27,9 +27,11 @@
 # vim: ft=zsh sw=2 ts=2 et
 # -------------------------------------------------------------------------------------------------
 
-BUFFER='ls highlighters/main/test-data/path-space-\ .zsh'
+mkdir A
+touch "A/mu with spaces"
+BUFFER='ls A/mu\ with\ spaces'
 
 expected_region_highlight=(
   "1 2  $ZSH_HIGHLIGHT_STYLES[command]" # ls
-  "4 48 $ZSH_HIGHLIGHT_STYLES[path]"    # highlighters/main/test-data/path-space-\ .zsh
+  "4 19 $ZSH_HIGHLIGHT_STYLES[path]"    # A/mu\ with\ spaces
 )

highlighters/main/test-data/path-tilde-named.zsh

@@ -27,11 +27,13 @@
 # vim: ft=zsh sw=2 ts=2 et
 # -------------------------------------------------------------------------------------------------
 
-hash -d D=highlighters/main/test-data
+mkdir mydir
+touch mydir/path-tilde-named.test
+hash -d D=mydir
 
-BUFFER='ls ~D/path-tilde-named.zsh'
+BUFFER='ls ~D/path-tilde-named.test'
 
 expected_region_highlight=(
   "1 2  $ZSH_HIGHLIGHT_STYLES[command]" # ls
-  "4 26 $ZSH_HIGHLIGHT_STYLES[path]"    # ~D/path-tilde-named.zsh
+  "4 27 $ZSH_HIGHLIGHT_STYLES[path]"    # ~D/path-tilde-named.test
 )

highlighters/main/test-data/path.zsh

@@ -27,9 +27,11 @@
 # vim: ft=zsh sw=2 ts=2 et
 # -------------------------------------------------------------------------------------------------
 
-BUFFER='ls highlighters/main/test-data/path.zsh'
+mkdir A
+touch A/mu
+BUFFER='ls A/mu'
 
 expected_region_highlight=(
   "1 2 $ZSH_HIGHLIGHT_STYLES[command]" # ls
-  "4 39 $ZSH_HIGHLIGHT_STYLES[path]"    # highlighters/main/test-data/path.zsh
+  "4 7 $ZSH_HIGHLIGHT_STYLES[path]"     # A/mu
 )

tests/README.md

@@ -17,7 +17,8 @@ _Note_: `$region_highlight` uses the same `"$i $j $style"` syntax but interprets
 
 **Isolation**: Each test is run in a separate subshell, so any variables, aliases, functions, etc.,
 it defines will be visible to the tested code (that computes `$region_highlight`), but will not affect
-subsequent tests.
+subsequent tests.  The current working directory of tests is set to a newly-created empty directory,
+which is automatically cleaned up after the test exits.
 
 
 highlighting test

tests/test-highlighting.zsh

@@ -55,15 +55,19 @@ ZSH_HIGHLIGHT_HIGHLIGHTERS=($1)
 
 # Runs a highlighting test
 # $1: data file
-run_test() {
+run_test_internal() {
   local -a highlight_zone
   local unused_highlight='bg=red,underline' # a style unused by anything else, for tests to use
 
+  local tests_tempdir="$1"; shift
+  local srcdir="$PWD"
+  builtin cd -q -- "$tests_tempdir" || { echo >&2 "Bail out! cd failed: $?"; return 1 }
+
   echo "# ${1:t:r}"
 
   # Load the data and prepare checking it.
   PREBUFFER= BUFFER= ;
-  . "$1"
+  . "$srcdir"/"$1"
 
   # Check the data declares $PREBUFFER or $BUFFER.
   [[ -z $PREBUFFER && -z $BUFFER ]] && { echo >&2 "Bail out! Either 'PREBUFFER' or 'BUFFER' must be declared and non-blank"; return 1; }
@@ -108,6 +112,21 @@ run_test() {
   done
 }
 
+run_test() {
+  # Do not combine the declaration and initialization: «local x="$(false)"» does not set $?.
+  local __tests_tempdir; __tests_tempdir="$(mktemp -d)"
+  if [[ $? -ne 0 ]] || [[ -z $__tests_tempdir ]] || [[ ! -d $__tests_tempdir ]]; then
+    echo >&2 "Bail out! mktemp failed"; return 1
+  fi
+  typeset -r __tests_tempdir # don't allow tests to override the variable that we will 'rm -rf' later on
+
+  {
+    run_test_internal "$__tests_tempdir" "$@"
+  } always {
+    rm -rf -- "$__tests_tempdir"
+  }
+}
+
 # Process each test data file in test data directory.
 integer something_failed=0
 for data_file in ${0:h:h}/highlighters/$1/test-data/*.zsh; do