Allow running specific high-level tests by passing the name to test.fish

Example:
  tests/test.fish expansion
This will run the tests in expansion.in only

tests/test.fish

@@ -2,7 +2,18 @@
 #
 # Fishscript tests
 
-source test_util.fish (status -f); or exit
+# Change to directory containing this script
+cd (dirname (status -f))
+
+# Test files specified on commandline, or all *.in files
+set -q argv[1]
+if set -q argv[1]
+    set files_to_test $argv.in
+else
+    set files_to_test *.in
+end
+
+source test_util.fish (status -f) $argv; or exit
 
 say -o cyan "Testing high level script functionality"
 
@@ -46,7 +57,7 @@ function test_file
 end
 
 set -l failed
-for i in *.in
+for i in $files_to_test
     if not test_file $i
         set failed $failed $i
     end

tests/test_util.fish

@@ -8,6 +8,12 @@ if test "$argv[1]" = (status -f)
     exit 1
 end
 
+# Any remaining arguments are passed back to test.fish
+set -l args_for_test_script
+if set -q argv[2]
+    set args_for_test_script $argv[2..-1]
+end
+
 function die
     set -q argv[1]; and echo $argv[1] >&2
     exit 1
@@ -51,7 +57,7 @@ if not set -q __fish_is_running_tests
         set -lx LC_$var ''
     end
     set -lx LC_CTYPE en_US.UTF-8
-    exec ../fish $script
+    exec ../fish $script $args_for_test_script
     die 'exec failed'
 else if test "$__fish_is_running_tests" != "$XDG_CONFIG_HOME"
     echo 'Something went wrong with the test runner.' >&2