diff --git a/tests/README.md b/tests/README.md
index 314dc606..76990a04 100644
--- a/tests/README.md
+++ b/tests/README.md
@@ -7,6 +7,8 @@ define a number of other macros to:
 - what skeleton is used
 
 # Keywords
+The following keywords are used to label tests.  Please follow them
+and avoid creating synonyms.
 - action
 - api.value.type
 - c++
@@ -24,3 +26,9 @@ define a number of other macros to:
 - report
 - %union
 - variant
+
+# Calculator
+The grammar features several special directives:
+- `!!` YYERROR
+- `!+` YYACCEPT
+- `!-` YYABORT
diff --git a/tests/calc.at b/tests/calc.at
index 005e6bee..2643d570 100644
--- a/tests/calc.at
+++ b/tests/calc.at
@@ -444,8 +444,10 @@ exp:
 | exp '^' exp        { $$ = power ($1, $3); }
 | '(' exp ')'        { $$ = $2; }
 | '(' error ')'      { $$ = 1111; yyerrok; }
-| '!'                { $$ = 0; YYERROR; }
 | '-' error          { $$ = 0; YYERROR; }
+| '!' '!'            { $$ = 0; YYERROR; }
+| '!' '+'            { $$ = 0; YYACCEPT; }
+| '!' '-'            { $$ = 0; YYABORT; }
 ;
 %%
 
@@ -727,8 +729,10 @@ exp:
 | exp "^" exp        { $$ = power ($1, $3); }
 | "(" exp ")"        { $$ = $2; }
 | "(" error ")"      { $$ = 1111; yyerrok(); }
-| "!"                { $$ = 0; return YYERROR; }
 | "-" error          { $$ = 0; return YYERROR; }
+| "!" "!"            { $$ = 0; return YYERROR; }
+| "!" "+"            { $$ = 0; return YYACCEPT; }
+| "!" "-"            { $$ = 0; return YYABORT; }
 ;
 %%
 
@@ -909,8 +913,10 @@ exp:
 | exp '^' exp        { $$ = (int) Math.pow ($1, $3); }
 | '(' exp ')'        { $$ = $2; }
 | '(' error ')'      { $$ = 1111; }
-| '!'                { $$ = 0; return YYERROR; }
 | '-' error          { $$ = 0; return YYERROR; }
+| '!' '!'            { $$ = 0; return YYERROR; }
+| '!' '+'            { $$ = 0; return YYACCEPT; }
+| '!' '-'            { $$ = 0; return YYABORT; }
 ;
 ]AT_CALC_YYLEX[
 ]AT_LOCATION_IF([[
@@ -953,6 +959,8 @@ m4_define([_AT_CHECK_CALC],
 [AT_DATA([[input]],
 [$2
 ])
+echo "input:"
+sed -e 's/^/  | /' <input
 AT_JAVA_IF(
   [AT_JAVA_PARSER_CHECK([Calc $1 < input], 0, [m4_ifvaln(m4_quote($3), [$3])], [stderr])],
   [AT_PARSER_CHECK([calc $1 input],        0, [m4_ifvaln(m4_quote($3), [$3])], [stderr])])
@@ -990,6 +998,8 @@ m4_define([_AT_CHECK_CALC_ERROR],
   [AT_DATA([[input]],
 [[$3
 ]])
+  echo "input:"
+  sed -e 's/^/  | /' <input
   AT_JAVA_IF(
     [AT_JAVA_PARSER_CHECK([Calc $7 < input], $2, [m4_ifvaln(m4_quote($4), [$4])], [stderr])],
     [AT_PARSER_CHECK([calc $7 input],        $2, [m4_ifvaln(m4_quote($4), [$4])], [stderr])])
@@ -1020,8 +1030,7 @@ mv at-stderr stderr
 
 # 2. Create the reference error message.
 AT_DATA([[expout]],
-[$6
-])
+[m4_n([$6])])
 
 # 3. If locations are not used, remove them.
 AT_YYERROR_SEES_LOC_IF([],
@@ -1190,11 +1199,11 @@ _AT_CHECK_CALC_ERROR([$1], [0],
 
 # The same, but this time exercising explicitly triggered syntax errors.
 # POSIX says the lookahead causing the error should not be discarded.
-_AT_CHECK_CALC_ERROR([$1], [0], [(!) + (1 2) = 1],
+_AT_CHECK_CALC_ERROR([$1], [0], [(!!) + (1 2) = 1],
                      [AT_PARAM_IF([final: 2222 0 2])],
                      [102],
-[AT_JAVA_IF([1.10-1.11], [1.10])[: syntax error on token [number] (expected: ['='] ['-'] ['+'] ['*'] ['/'] ['^'] [')'])
-]AT_JAVA_IF([1.1-1.16], [1.1-15])[: error: 2222 != 1]])
+[AT_JAVA_IF([1.11-1.12], [1.11])[: syntax error on token [number] (expected: ['='] ['-'] ['+'] ['*'] ['/'] ['^'] [')'])
+]AT_JAVA_IF([1.1-1.17], [1.1-16])[: error: 2222 != 1]])
 
 _AT_CHECK_CALC_ERROR([$1], [0], [(- *) + (1 2) = 1],
                      [AT_PARAM_IF([final: 2222 0 3])],
@@ -1213,6 +1222,24 @@ _AT_CHECK_CALC_ERROR([$1], [0], [(* *) + (*) + (*)],
 ]AT_JAVA_IF([1.16-1.17], [1.16])[: syntax error on token ['*'] (expected: [number] ['-'] ['('] ['!'])]])
 
 
+# Special actions.
+# ----------------
+# !+ => YYACCEPT, !- => YYABORT, !! => YYERROR.
+
+# YYACCEPT.
+# Java lacks the traces at the end for cleaning the stack
+# -Stack now 0 8 20
+# -Cleanup: popping token '+' (1.1: )
+# -Cleanup: popping nterm exp (1.1: 7)
+_AT_CHECK_CALC([], [1 + 2 * 3 + !+ ++],
+               [AT_PARAM_IF([final: 0 0 0])],
+               [AT_JAVA_IF([77], [80])])
+# YYABORT.
+_AT_CHECK_CALC_ERROR([$1], [1], [1 + 2 * 3 + !- ++],
+                     [AT_PARAM_IF([final: 0 0 0])],
+                     [102])
+
+
 # YYerror.
 # --------
 # Check that returning YYerror from the scanner properly enters