在Mocha / Chai测试中进行测试时是否可能出现SyntaxErrors？

Question

我有一个文件，其中包含有关如何根据SyntaxError类型处理SyntaxErrors的代码，它是一个解析文件。但是，由于SyntaxErrors，测试最终失败。我需要找到一种方法来覆盖解析文件中的这些代码行，而又不能使测试失败。是否可以为我的mocha / chai测试设置某种标志以允许SyntaxError测试通过？解析器文件是从PEG.js生成的，因此，我尽量避免更改解析器文件。任何帮助将不胜感激。

这里是解析文件的示例：

module.exports = /*
 * Generated by PEG.js 0.10.0.
 *
 * http://pegjs.org/
 */
(function() {
  "use strict";

  function peg$subclass(child, parent) {
    function ctor() { this.constructor = child; }
    ctor.prototype = parent.prototype;
    child.prototype = new ctor();
  }

  function peg$SyntaxError(message, expected, found, location) {
    this.message  = message;
    this.expected = expected;
    this.found    = found;
    this.location = location;
    this.name     = "SyntaxError";

    if (typeof Error.captureStackTrace === "function") {
      Error.captureStackTrace(this, peg$SyntaxError);
    }
  }

  peg$subclass(peg$SyntaxError, Error);

  peg$SyntaxError.buildMessage = function(expected, found) {
    var DESCRIBE_EXPECTATION_FNS = {
          literal: function(expectation) {
            return "\"" + literalEscape(expectation.text) + "\"";
          },

          "class": function(expectation) {
            var escapedParts = "",
                i;

            for (i = 0; i < expectation.parts.length; i++) {
              escapedParts += expectation.parts[i] instanceof Array
                ? classEscape(expectation.parts[i][0]) + "-" + classEscape(expectation.parts[i][1])
                : classEscape(expectation.parts[i]);
            }

            return "[" + (expectation.inverted ? "^" : "") + escapedParts + "]";
          },

          any: function(expectation) {
            return "any character";
          },

          end: function(expectation) {
            return "end of input";
          },

          other: function(expectation) {
            return expectation.description;
          }
        };

    function hex(ch) {
      return ch.charCodeAt(0).toString(16).toUpperCase();
    }

    function literalEscape(s) {
      return s
        .replace(/\\/g, '\\\\')
        .replace(/"/g,  '\\"')
        .replace(/\0/g, '\\0')
        .replace(/\t/g, '\\t')
        .replace(/\n/g, '\\n')
        .replace(/\r/g, '\\r')
        .replace(/[\x00-\x0F]/g,          function(ch) { return '\\x0' + hex(ch); })
        .replace(/[\x10-\x1F\x7F-\x9F]/g, function(ch) { return '\\x'  + hex(ch); });
    }

    function classEscape(s) {
      return s
        .replace(/\\/g, '\\\\')
        .replace(/\]/g, '\\]')
        .replace(/\^/g, '\\^')
        .replace(/-/g,  '\\-')
        .replace(/\0/g, '\\0')
        .replace(/\t/g, '\\t')
        .replace(/\n/g, '\\n')
        .replace(/\r/g, '\\r')
        .replace(/[\x00-\x0F]/g,          function(ch) { return '\\x0' + hex(ch); })
        .replace(/[\x10-\x1F\x7F-\x9F]/g, function(ch) { return '\\x'  + hex(ch); });
    }

    function describeExpectation(expectation) {
      return DESCRIBE_EXPECTATION_FNS[expectation.type](expectation);
    }

    function describeExpected(expected) {
      var descriptions = new Array(expected.length),
          i, j;

      for (i = 0; i < expected.length; i++) {
        descriptions[i] = describeExpectation(expected[i]);
      }

      descriptions.sort();

      if (descriptions.length > 0) {
        for (i = 1, j = 1; i < descriptions.length; i++) {
          if (descriptions[i - 1] !== descriptions[i]) {
            descriptions[j] = descriptions[i];
            j++;
          }
        }
        descriptions.length = j;
      }

      switch (descriptions.length) {
        case 1:
          return descriptions[0];

        case 2:
          return descriptions[0] + " or " + descriptions[1];

        default:
          return descriptions.slice(0, -1).join(", ")
            + ", or "
            + descriptions[descriptions.length - 1];
      }
    }

    function describeFound(found) {
      return found ? "\"" + literalEscape(found) + "\"" : "end of input";
    }

    return "Expected " + describeExpected(expected) + " but " + describeFound(found) + " found.";
  };

  function peg$parse(input, options) {
    options = options !== void 0 ? options : {};

    var peg$FAILED = {},

        peg$startRuleFunctions = { Expression: peg$parseExpression },
        peg$startRuleFunction  = peg$parseExpression,

        peg$c0 = function(accessors) {return accessors;},
        peg$c1 = function(property) {return property;},
        peg$c2 = /^[[]/,
        peg$c3 = peg$classExpectation(["["], false, false),
        peg$c4 = "CURRENT_LINE",
        peg$c5 = peg$literalExpectation("CURRENT_LINE", false),
        peg$c6 = /^[\]]/,
        peg$c7 = peg$classExpectation(["]"], false, false),
        peg$c8 = /^[.]/,
        peg$c9 = peg$classExpectation(["."], false, false),
        peg$c10 = function(variable, type) { return variable+'['+type+']';},
        peg$c11 = "ALL_LINES",
        peg$c12 = peg$literalExpectation("ALL_LINES", false),
        peg$c13 = "ANY_LINES",
        peg$c14 = peg$literalExpectation("ANY_LINES", false),
        peg$c15 = "ALL_PENDED_LINES",
        peg$c16 = peg$literalExpectation("ALL_PENDED_LINES", false),
        peg$c17 = "ANY_PENDED_LINES",
        peg$c18 = peg$literalExpectation("ANY_PENDED_LINES", false),
        peg$c19 = "FIRST_PENDED_LINE",
        peg$c20 = peg$literalExpectation("FIRST_PENDED_LINE", false),
        peg$c21 = function(variable, int) { return variable+'['+int+']' },
        peg$c22 = "0",
        peg$c23 = peg$literalExpectation("0", false),
        peg$c24 = function(variable, int) { if(int.length!=0){return {array:variable+'['+int+']'};} else {return {array:variable+'[0]'};} },
        peg$c25 = function(variable, period) { return variable;},
        peg$c26 = "substring(",
        peg$c27 = peg$literalExpectation("substring(", false),
        peg$c28 = ",",
        peg$c29 = peg$literalExpectation(",", false),
        peg$c30 = ")",
        peg$c31 = peg$literalExpectation(")", false),
        peg$c32 = function(index1, index2) {return 'substring('+index1+','+index2+')';},
        peg$c33 = function(index1) {return 'substring('+index1+')';},
        peg$c34 = /^[a-zA-Z0-9_]/,
        peg$c35 = peg$classExpectation([["a", "z"], ["A", "Z"], ["0", "9"], "_"], false, false),
        peg$c36 = function(v) { return v.join(""); },
        peg$c37 = peg$otherExpectation("integer"),
        peg$c38 = /^[0-9]/,
        peg$c39 = peg$classExpectation([["0", "9"]], false, false),
        peg$c40 = function() { return parseInt(text(), 10); },
        peg$c41 = peg$otherExpectation("whitespace"),
        peg$c42 = /^[ \t\n\r]/,
        peg$c43 = peg$classExpectation([" ", "\t", "\n", "\r"], false, false),

        peg$currPos          = 0,
        peg$savedPos         = 0,
        peg$posDetailsCache  = [{ line: 1, column: 1 }],
        peg$maxFailPos       = 0,
        peg$maxFailExpected  = [],
        peg$silentFails      = 0,

        peg$resultsCache = {},

        peg$result;

    if ("startRule" in options) {
      if (!(options.startRule in peg$startRuleFunctions)) {
        throw new Error("Can't start parsing from rule \"" + options.startRule + "\".");
      }

      peg$startRuleFunction = peg$startRuleFunctions[options.startRule];
    }

    function text() {
      return input.substring(peg$savedPos, peg$currPos);
    }

    function location() {
      return peg$computeLocation(peg$savedPos, peg$currPos);
    }

    function expected(description, location) {
      location = location !== void 0 ? location : peg$computeLocation(peg$savedPos, peg$currPos)

      throw peg$buildStructuredError(
        [peg$otherExpectation(description)],
        input.substring(peg$savedPos, peg$currPos),
        location
      );
    }

    function error(message, location) {
      location = location !== void 0 ? location : peg$computeLocation(peg$savedPos, peg$currPos)

      throw peg$buildSimpleError(message, location);
    }

    function peg$literalExpectation(text, ignoreCase) {
      return { type: "literal", text: text, ignoreCase: ignoreCase };
    }

    function peg$classExpectation(parts, inverted, ignoreCase) {
      return { type: "class", parts: parts, inverted: inverted, ignoreCase: ignoreCase };
    }

    function peg$anyExpectation() {
      return { type: "any" };
    }

    function peg$endExpectation() {
      return { type: "end" };
    }

    function peg$otherExpectation(description) {
      return { type: "other", description: description };
    }

    function peg$computePosDetails(pos) {
      var details = peg$posDetailsCache[pos], p;

      if (details) {
        return details;
      } else {
        p = pos - 1;
        while (!peg$posDetailsCache[p]) {
          p--;
        }

        details = peg$posDetailsCache[p];
        details = {
          line:   details.line,
          column: details.column
        };

        while (p < pos) {
          if (input.charCodeAt(p) === 10) {
            details.line++;
            details.column = 1;
          } else {
            details.column++;
          }

          p++;
        }

        peg$posDetailsCache[pos] = details;
        return details;
      }
    }

    function peg$computeLocation(startPos, endPos) {
      var startPosDetails = peg$computePosDetails(startPos),
          endPosDetails   = peg$computePosDetails(endPos);

      return {
        start: {
          offset: startPos,
          line:   startPosDetails.line,
          column: startPosDetails.column
        },
        end: {
          offset: endPos,
          line:   endPosDetails.line,
          column: endPosDetails.column
        }
      };
    }

    function peg$fail(expected) {
      if (peg$currPos < peg$maxFailPos) { return; }

      if (peg$currPos > peg$maxFailPos) {
        peg$maxFailPos = peg$currPos;
        peg$maxFailExpected = [];
      }

      peg$maxFailExpected.push(expected);
    }

    function peg$buildSimpleError(message, location) {
      return new peg$SyntaxError(message, null, null, location);
    }

    function peg$buildStructuredError(expected, found, location) {
      return new peg$SyntaxError(
        peg$SyntaxError.buildMessage(expected, found),
        expected,
        found,
        location
      );
    }

    function peg$parseExpression() {
      var s0, s1, s2, s3;

      var key    = peg$currPos * 9 + 0,
          cached = peg$resultsCache[key];

      if (cached) {
        peg$currPos = cached.nextPos;

        return cached.result;
      }

      s0 = peg$currPos;
      s1 = peg$parse_();
      if (s1 !== peg$FAILED) {
        s2 = [];
        s3 = peg$parseAccessors();
        if (s3 !== peg$FAILED) {
          while (s3 !== peg$FAILED) {
            s2.push(s3);
            s3 = peg$parseAccessors();
          }
        } else {
          s2 = peg$FAILED;
        }
        if (s2 !== peg$FAILED) {
          s3 = peg$parse_();
          if (s3 !== peg$FAILED) {
            peg$savedPos = s0;
            s1 = peg$c0(s2);
            s0 = s1;
          } else {
            peg$currPos = s0;
            s0 = peg$FAILED;
          }
        } else {
          peg$currPos = s0;
          s0 = peg$FAILED;
        }
      } else {
        peg$currPos = s0;
        s0 = peg$FAILED;
      }

      peg$resultsCache[key] = { nextPos: peg$currPos, result: s0 };

      return s0;
    }

    function peg$parseAccessors() {
      var s0, s1;

      var key    = peg$currPos * 9 + 1,
          cached = peg$resultsCache[key];

      if (cached) {
        peg$currPos = cached.nextPos;

        return cached.result;
      }

      s0 = peg$parsePropertyArray();
      if (s0 === peg$FAILED) {
        s0 = peg$parseSpecialArray();
        if (s0 === peg$FAILED) {
          s0 = peg$parseSubstringFunction();
          if (s0 === peg$FAILED) {
            s0 = peg$currPos;
            s1 = peg$parseProperty();
            if (s1 !== peg$FAILED) {
              peg$savedPos = s0;
              s1 = peg$c1(s1);
            }
            s0 = s1;
          }
        }
      }

      peg$resultsCache[key] = { nextPos: peg$currPos, result: s0 };

      return s0;
    }

    function peg$parseSpecialArray() {
      var s0, s1, s2, s3, s4, s5, s6;

      var key    = peg$currPos * 9 + 2,
          cached = peg$resultsCache[key];

      if (cached) {
        peg$currPos = cached.nextPos;

        return cached.result;
      }

      s0 = peg$currPos;
      s1 = peg$parseVariable();
      if (s1 !== peg$FAILED) {
        if (peg$c2.test(input.charAt(peg$currPos))) {
          s2 = input.charAt(peg$currPos);
          peg$currPos++;
        } else {
          s2 = peg$FAILED;
          if (peg$silentFails === 0) { peg$fail(peg$c3); }
        }
        if (s2 !== peg$FAILED) {
          if (input.substr(peg$currPos, 12) === peg$c4) {
            s3 = peg$c4;
            peg$currPos += 12;
          } else {
            s3 = peg$FAILED;
            if (peg$silentFails === 0) { peg$fail(peg$c5); }
          }
          if (s3 !== peg$FAILED) {
            if (peg$c6.test(input.charAt(peg$currPos))) {
              s4 = input.charAt(peg$currPos);
              peg$currPos++;
            } else {
              s4 = peg$FAILED;
              if (peg$silentFails === 0) { peg$fail(peg$c7); }
            }
            if (s4 !== peg$FAILED) {
              if (peg$c8.test(input.charAt(peg$currPos))) {
                s5 = input.charAt(peg$currPos);
                peg$currPos++;
              } else {
                s5 = peg$FAILED;
                if (peg$silentFails === 0) { peg$fail(peg$c9); }
              }
              if (s5 !== peg$FAILED) {
                peg$savedPos = s0;
                s1 = peg$c10(s1, s3);
                s0 = s1;
              } else {
                peg$currPos = s0;
                s0 = peg$FAILED;
              }
            } else {
              peg$currPos = s0;
              s0 = peg$FAILED;
            }
          } else {
            peg$currPos = s0;
            s0 = peg$FAILED;
          }
        } else {
          peg$currPos = s0;
          s0 = peg$FAILED;
        }
      } else {
        peg$currPos = s0;
        s0 = peg$FAILED;
      }
      if (s0 === peg$FAILED) {
        s0 = peg$currPos;
        s1 = peg$parseVariable();
        if (s1 !== peg$FAILED) {
          if (peg$c2.test(input.charAt(peg$currPos))) {
            s2 = input.charAt(peg$currPos);
            peg$currPos++;
          } else {
            s2 = peg$FAILED;
            if (peg$silentFails === 0) { peg$fail(peg$c3); }
          }
          if (s2 !== peg$FAILED) {
            if (input.substr(peg$currPos, 9) === peg$c11) {
              s3 = peg$c11;
              peg$currPos += 9;
            } else {
              s3 = peg$FAILED;
              if (peg$silentFails === 0) { peg$fail(peg$c12); }
            }
            if (s3 !== peg$FAILED) {
              if (peg$c6.test(input.charAt(peg$currPos))) {
                s4 = input.charAt(peg$currPos);
                peg$currPos++;
              } else {
                s4 = peg$FAILED;
                if (peg$silentFails === 0) { peg$fail(peg$c7); }
              }
              if (s4 !== peg$FAILED) {

注意：由于字符限制，删除了某些文件内容

Answer 1

您可以使用try/catch语句来捕获解析错误。或者，您可以使用Mocha断言expect(fn).to.throw()。