Add support for bubbling up skipped tests to cmake

This prevents tests that were skipped (e.g. because of a missing
REQUIRES) from being reported as successes in the CTest overall run
results list.

tests/test.fish

@@ -19,27 +19,40 @@ else
     set files_to_test checks/*.fish
 end
 
-say -o cyan "Testing high level script functionality"
+# Be less verbose when running tests one-by-one
+if test (count $files_to_test) -gt 1
+    say -o cyan "Testing high level script functionality"
+end
 
 set -g python (__fish_anypython)
 
 # Test littlecheck files.
-set littlecheck_files (string match '*.fish' -- $files_to_test)
-if set -q littlecheck_files[1]
+set -l skipped 0
+set -l failed 0
+if set -q files_to_test[1]
     $python -S ../littlecheck.py \
         --progress \
         -s fish=../test/root/bin/fish \
         -s fish_test_helper=../test/root/bin/fish_test_helper \
-        $littlecheck_files
-    set -l littlecheck_failures $status
-    set failed (math $failed + $littlecheck_failures)
+        $files_to_test
+
+    set -l littlecheck_status $status
+    if test "$littlecheck_status" -eq 125
+        # 125 indicates that all tests executed were skipped.
+        set skipped (count $files_to_test)
+    else
+        # The return code indicates the number of tests that failed
+        set failed $littlecheck_status
+    end
 end
 
-if test $failed -eq 0
-    say green "All high level script tests completed successfully"
+if test $failed -eq 0 && test $skipped -gt 0
+    test (count $files_to_test) -gt 1 && say blue (count $files_to_test)" tests skipped"
+    exit 125
+else if test $failed -eq 0
+    test (count $files_to_test) -gt 1 && say green "All high level script tests completed successfully"
     exit 0
 else
-    set plural (test $failed -eq 1; or echo s)
-    say red "$failed test$plural failed"
+    test (count $files_to_test) -gt 1 && say red "$failed tests failed"
     exit 1
 end