anchor.diff:          .add([Token('10', TokenType.VAL), Token('tan', TokenType.TAN)]);
   
       // Arccos
  -    inputStrings.add('arccos(10)');
  +    inputStrings.add('arccos(1)');
       tokenStreams.add([
         Token('arccos', TokenType.ACOS),
         Token('(', TokenType.LBRACE),
  -      Token('10', TokenType.VAL),
  -      Token(')', TokenType.RBRACE)
  -    ]);
  -    rpnTokenStreams
  -        .add([Token('10', TokenType.VAL), Token('arccos', TokenType.ACOS)]);
  +      Token('1', TokenType.VAL),
  +      Token(')', TokenType.RBRACE)
  +    ]);
  +    rpnTokenStreams
  +        .add([Token('1', TokenType.VAL), Token('arccos', TokenType.ACOS)]);
   
       // Arcsin
  -    inputStrings.add('arcsin(10)');
  +    inputStrings.add('arcsin(1)');
       tokenStreams.add([
         Token('arcsin', TokenType.ASIN),
         Token('(', TokenType.LBRACE),
  -      Token('10', TokenType.VAL),
  -      Token(')', TokenType.RBRACE)
  -    ]);
  -    rpnTokenStreams
  -        .add([Token('10', TokenType.VAL), Token('arcsin', TokenType.ASIN)]);
  +      Token('1', TokenType.VAL),
  +      Token(')', TokenType.RBRACE)
  +    ]);
  +    rpnTokenStreams
  +        .add([Token('1', TokenType.VAL), Token('arcsin', TokenType.ASIN)]);
   
       // Arctan
       inputStrings.add('arctan(10)');
  
positive.code:         'Lexer Tokenize (Infix + Postfix)': lexerTokenTest,
          'Lexer Tokenize Invalid': lexerTokenTestInvalid,
          'Parser Expression Creation': parserExpressionTest,
          'Parser Expression Creation Invalid': parserExpressionTestInvalid
        };
  
    @override
  
negative.code:       expect(() => pars.parse(expr), invalidCases[expr]);
      }
    }
  
    void parserExpressionTest_ParseFromToString() {
      ContextModel context = ContextModel()
        ..bindVariableName('x', Number(math.pi));
  
      for (String inputString in inputStrings) {
        /// Expression doesn't implement equal, so as an approximation
        /// we're testing whether the expression re-parses and evaluates
        /// to the same value.
        Expression exp = pars.parse(inputString);
  
        try {
          Expression exp2 = pars.parse(exp.toString());
  
          double r1 = exp.evaluate(EvaluationType.REAL, context);
          double r2 = exp2.evaluate(EvaluationType.REAL, context);
          expect(r2, r1, reason: 'Expected ${r2} for ${exp} (${exp2})');
        } on FormatException catch (fe) {
          expect(fe, isNot(isFormatException),
              reason: 'Expected no exception for ${inputString} (${exp})');
        } on RangeError catch (re) {
          expect(re, isNot(isRangeError),
              reason: 'Expected no exception for ${inputString} (${exp})');
        }
      }
    }
  }
  