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Testing Core Utility Functions in Mozilla PDF.js

This test suite evaluates core utility functions in Mozilla’s pdf.js library, focusing on data manipulation, string encoding, and PDF-specific operations. The tests verify essential functionality for handling PDF content including array buffers, property inheritance, number formatting, and string validation.
Test Coverage Overview

The test suite provides comprehensive coverage of core utility functions essential for PDF processing:
Array buffer manipulation and byte conversion
Property inheritance and dictionary handling
Number formatting and conversion utilities
String validation and encoding for PDF content
XML and CSS font validation
Implementation Analysis

The testing approach uses Jasmine’s describe/it pattern for structured unit testing. Each utility function is tested independently with multiple test cases covering normal operations, edge cases, and error conditions. The implementation leverages mock objects (XRefMock) to simulate PDF document structures.
Technical Details

Testing tools and setup:
Jasmine test framework for behavior-driven development
Mock objects for XRef handling
Custom Dict and Ref implementations
UTF-16 encoding validation
CSS font validation utilities
Best Practices Demonstrated

The test suite exhibits several testing best practices:
Comprehensive edge case handling
Isolated function testing
Clear test case descriptions
Structured test organization
Mock object usage for dependencies
mozilla/pdfJs

test/unit/core_utils_spec.js
            
/* Copyright 2019 Mozilla Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import {
  arrayBuffersToBytes,
  encodeToXmlString,
  escapePDFName,
  escapeString,
  getInheritableProperty,
  getSizeInBytes,
  isAscii,
  isWhiteSpace,
  log2,
  numberToString,
  parseXFAPath,
  recoverJsURL,
  stringToUTF16HexString,
  stringToUTF16String,
  toRomanNumerals,
  validateCSSFont,
} from "../../src/core/core_utils.js";
import { Dict, Ref } from "../../src/core/primitives.js";
import { XRefMock } from "./test_utils.js";

describe("core_utils", function () {
  describe("arrayBuffersToBytes", function () {
    it("handles zero ArrayBuffers", function () {
      const bytes = arrayBuffersToBytes([]);

      expect(bytes).toEqual(new Uint8Array(0));
    });

    it("handles one ArrayBuffer", function () {
      const buffer = new Uint8Array([1, 2, 3]).buffer;
      const bytes = arrayBuffersToBytes([buffer]);

      expect(bytes).toEqual(new Uint8Array([1, 2, 3]));
      // Ensure that the fast-path works correctly.
      expect(bytes.buffer).toBe(buffer);
    });

    it("handles multiple ArrayBuffers", function () {
      const buffer1 = new Uint8Array([1, 2, 3]).buffer,
        buffer2 = new Uint8Array(0).buffer,
        buffer3 = new Uint8Array([4, 5]).buffer;
      const bytes = arrayBuffersToBytes([buffer1, buffer2, buffer3]);

      expect(bytes).toEqual(new Uint8Array([1, 2, 3, 4, 5]));
    });
  });

  describe("getInheritableProperty", function () {
    it("handles non-dictionary arguments", function () {
      expect(getInheritableProperty({ dict: null, key: "foo" })).toEqual(
        undefined
      );
      expect(getInheritableProperty({ dict: undefined, key: "foo" })).toEqual(
        undefined
      );
    });

    it("handles dictionaries that do not contain the property", function () {
      // Empty dictionary.
      const emptyDict = new Dict();
      expect(getInheritableProperty({ dict: emptyDict, key: "foo" })).toEqual(
        undefined
      );

      // Filled dictionary with a different property.
      const filledDict = new Dict();
      filledDict.set("bar", "baz");
      expect(getInheritableProperty({ dict: filledDict, key: "foo" })).toEqual(
        undefined
      );
    });

    it("fetches the property if it is not inherited", function () {
      const ref = Ref.get(10, 0);
      const xref = new XRefMock([{ ref, data: "quux" }]);
      const dict = new Dict(xref);

      // Regular values should be fetched.
      dict.set("foo", "bar");
      expect(getInheritableProperty({ dict, key: "foo" })).toEqual("bar");

      // Array value should be fetched (with references resolved).
      dict.set("baz", ["qux", ref]);
      expect(
        getInheritableProperty({ dict, key: "baz", getArray: true })
      ).toEqual(["qux", "quux"]);
    });

    it("fetches the property if it is inherited and present on one level", function () {
      const ref = Ref.get(10, 0);
      const xref = new XRefMock([{ ref, data: "quux" }]);
      const firstDict = new Dict(xref);
      const secondDict = new Dict(xref);
      firstDict.set("Parent", secondDict);

      // Regular values should be fetched.
      secondDict.set("foo", "bar");
      expect(getInheritableProperty({ dict: firstDict, key: "foo" })).toEqual(
        "bar"
      );

      // Array value should be fetched (with references resolved).
      secondDict.set("baz", ["qux", ref]);
      expect(
        getInheritableProperty({ dict: firstDict, key: "baz", getArray: true })
      ).toEqual(["qux", "quux"]);
    });

    it("fetches the property if it is inherited and present on multiple levels", function () {
      const ref = Ref.get(10, 0);
      const xref = new XRefMock([{ ref, data: "quux" }]);
      const firstDict = new Dict(xref);
      const secondDict = new Dict(xref);
      firstDict.set("Parent", secondDict);

      // Regular values should be fetched.
      firstDict.set("foo", "bar1");
      secondDict.set("foo", "bar2");
      expect(getInheritableProperty({ dict: firstDict, key: "foo" })).toEqual(
        "bar1"
      );
      expect(
        getInheritableProperty({
          dict: firstDict,
          key: "foo",
          getArray: false,
          stopWhenFound: false,
        })
      ).toEqual(["bar1", "bar2"]);

      // Array value should be fetched (with references resolved).
      firstDict.set("baz", ["qux1", ref]);
      secondDict.set("baz", ["qux2", ref]);
      expect(
        getInheritableProperty({
          dict: firstDict,
          key: "baz",
          getArray: true,
          stopWhenFound: false,
        })
      ).toEqual([
        ["qux1", "quux"],
        ["qux2", "quux"],
      ]);
    });
  });

  describe("toRomanNumerals", function () {
    it("handles invalid arguments", function () {
      for (const input of ["foo", -1, 0]) {
        expect(function () {
          toRomanNumerals(input);
        }).toThrow(new Error("The number should be a positive integer."));
      }
    });

    it("converts numbers to uppercase Roman numerals", function () {
      expect(toRomanNumerals(1)).toEqual("I");
      expect(toRomanNumerals(6)).toEqual("VI");
      expect(toRomanNumerals(7)).toEqual("VII");
      expect(toRomanNumerals(8)).toEqual("VIII");
      expect(toRomanNumerals(10)).toEqual("X");
      expect(toRomanNumerals(40)).toEqual("XL");
      expect(toRomanNumerals(100)).toEqual("C");
      expect(toRomanNumerals(500)).toEqual("D");
      expect(toRomanNumerals(1000)).toEqual("M");
      expect(toRomanNumerals(2019)).toEqual("MMXIX");
    });

    it("converts numbers to lowercase Roman numerals", function () {
      expect(toRomanNumerals(1, /* lowercase = */ true)).toEqual("i");
      expect(toRomanNumerals(6, /* lowercase = */ true)).toEqual("vi");
      expect(toRomanNumerals(7, /* lowercase = */ true)).toEqual("vii");
      expect(toRomanNumerals(8, /* lowercase = */ true)).toEqual("viii");
      expect(toRomanNumerals(10, /* lowercase = */ true)).toEqual("x");
      expect(toRomanNumerals(40, /* lowercase = */ true)).toEqual("xl");
      expect(toRomanNumerals(100, /* lowercase = */ true)).toEqual("c");
      expect(toRomanNumerals(500, /* lowercase = */ true)).toEqual("d");
      expect(toRomanNumerals(1000, /* lowercase = */ true)).toEqual("m");
      expect(toRomanNumerals(2019, /* lowercase = */ true)).toEqual("mmxix");
    });
  });

  describe("log2", function () {
    it("handles values smaller than/equal to zero", function () {
      expect(log2(0)).toEqual(0);
      expect(log2(-1)).toEqual(0);
    });

    it("handles values larger than zero", function () {
      expect(log2(1)).toEqual(0);
      expect(log2(2)).toEqual(1);
      expect(log2(3)).toEqual(2);
      expect(log2(3.14)).toEqual(2);
    });
  });

  describe("numberToString", function () {
    it("should stringify integers", function () {
      expect(numberToString(1)).toEqual("1");
      expect(numberToString(0)).toEqual("0");
      expect(numberToString(-1)).toEqual("-1");
    });

    it("should stringify floats", function () {
      expect(numberToString(1.0)).toEqual("1");
      expect(numberToString(1.2)).toEqual("1.2");
      expect(numberToString(1.23)).toEqual("1.23");
      expect(numberToString(1.234)).toEqual("1.23");
    });
  });

  describe("isWhiteSpace", function () {
    it("handles space characters", function () {
      expect(isWhiteSpace(0x20)).toEqual(true);
      expect(isWhiteSpace(0x09)).toEqual(true);
      expect(isWhiteSpace(0x0d)).toEqual(true);
      expect(isWhiteSpace(0x0a)).toEqual(true);
    });

    it("handles non-space characters", function () {
      expect(isWhiteSpace(0x0b)).toEqual(false);
      expect(isWhiteSpace(null)).toEqual(false);
      expect(isWhiteSpace(undefined)).toEqual(false);
    });
  });

  describe("parseXFAPath", function () {
    it("should get a correctly parsed path", function () {
      const path = "foo.bar[12].oof[3].rab.FOO[123].BAR[456]";
      expect(parseXFAPath(path)).toEqual([
        { name: "foo", pos: 0 },
        { name: "bar", pos: 12 },
        { name: "oof", pos: 3 },
        { name: "rab", pos: 0 },
        { name: "FOO", pos: 123 },
        { name: "BAR", pos: 456 },
      ]);
    });
  });

  describe("recoverJsURL", function () {
    it("should get valid URLs without `newWindow` property", function () {
      const inputs = [
        "window.open('https://test.local')",
        "window.open('https://test.local', true)",
        "app.launchURL('https://test.local')",
        "app.launchURL('https://test.local', false)",
        "xfa.host.gotoURL('https://test.local')",
        "xfa.host.gotoURL('https://test.local', true)",
      ];

      for (const input of inputs) {
        expect(recoverJsURL(input)).toEqual({
          url: "https://test.local",
          newWindow: false,
        });
      }
    });

    it("should get valid URLs with `newWindow` property", function () {
      const input = "app.launchURL('https://test.local', true)";
      expect(recoverJsURL(input)).toEqual({
        url: "https://test.local",
        newWindow: true,
      });
    });

    it("should not get invalid URLs", function () {
      const input = "navigateToUrl('https://test.local')";
      expect(recoverJsURL(input)).toBeNull();
    });
  });

  describe("escapePDFName", function () {
    it("should escape PDF name", function () {
      expect(escapePDFName("hello")).toEqual("hello");
      expect(escapePDFName("\xfehello")).toEqual("#fehello");
      expect(escapePDFName("he\xfell\xffo")).toEqual("he#fell#ffo");
      expect(escapePDFName("\xfehe\xfell\xffo\xff")).toEqual(
        "#fehe#fell#ffo#ff"
      );
      expect(escapePDFName("#h#e#l#l#o")).toEqual("#23h#23e#23l#23l#23o");
      expect(escapePDFName("#()<>[]{}/%")).toEqual(
        "#23#28#29#3c#3e#5b#5d#7b#7d#2f#25"
      );
    });
  });

  describe("escapeString", function () {
    it("should escape (, ), \\n, \\r, and \\", function () {
      expect(escapeString("((a\\a))\n(b(b\\b)\rb)")).toEqual(
        "\\(\\(a\\\\a\\)\\)\\n\\(b\\(b\\\\b\\)\\rb\\)"
      );
    });
  });

  describe("encodeToXmlString", function () {
    it("should get a correctly encoded string with some entities", function () {
      const str = "\"\u0397ell😂' & <W😂rld>";
      expect(encodeToXmlString(str)).toEqual(
        ""Ηell😂&apos; & <W😂rld>"
      );
    });

    it("should get a correctly encoded basic ascii string", function () {
      const str = "hello world";
      expect(encodeToXmlString(str)).toEqual(str);
    });
  });

  describe("validateCSSFont", function () {
    it("Check font family", function () {
      const cssFontInfo = {
        fontFamily: `"blah blah " blah blah"`,
        fontWeight: 0,
        italicAngle: 0,
      };

      expect(validateCSSFont(cssFontInfo)).toEqual(false);

      cssFontInfo.fontFamily = `"blah blah \\" blah blah"`;
      expect(validateCSSFont(cssFontInfo)).toEqual(true);

      cssFontInfo.fontFamily = `'blah blah ' blah blah'`;
      expect(validateCSSFont(cssFontInfo)).toEqual(false);

      cssFontInfo.fontFamily = `'blah blah \\' blah blah'`;
      expect(validateCSSFont(cssFontInfo)).toEqual(true);

      cssFontInfo.fontFamily = `"blah blah `;
      expect(validateCSSFont(cssFontInfo)).toEqual(false);

      cssFontInfo.fontFamily = `blah blah"`;
      expect(validateCSSFont(cssFontInfo)).toEqual(false);

      cssFontInfo.fontFamily = `'blah blah `;
      expect(validateCSSFont(cssFontInfo)).toEqual(false);

      cssFontInfo.fontFamily = `blah blah'`;
      expect(validateCSSFont(cssFontInfo)).toEqual(false);

      cssFontInfo.fontFamily = "blah blah blah";
      expect(validateCSSFont(cssFontInfo)).toEqual(true);

      cssFontInfo.fontFamily = "blah 0blah blah";
      expect(validateCSSFont(cssFontInfo)).toEqual(false);

      cssFontInfo.fontFamily = "blah blah -0blah";
      expect(validateCSSFont(cssFontInfo)).toEqual(false);

      cssFontInfo.fontFamily = "blah blah --blah";
      expect(validateCSSFont(cssFontInfo)).toEqual(false);

      cssFontInfo.fontFamily = "blah blah -blah";
      expect(validateCSSFont(cssFontInfo)).toEqual(true);

      cssFontInfo.fontFamily = "blah fdqAJqjHJK23kl23__--Kj blah";
      expect(validateCSSFont(cssFontInfo)).toEqual(true);

      cssFontInfo.fontFamily = "blah fdqAJqjH$JK23kl23__--Kj blah";
      expect(validateCSSFont(cssFontInfo)).toEqual(false);
    });

    it("Check font weight", function () {
      const cssFontInfo = {
        fontFamily: "blah",
        fontWeight: 100,
        italicAngle: 0,
      };

      validateCSSFont(cssFontInfo);
      expect(cssFontInfo.fontWeight).toEqual("100");

      cssFontInfo.fontWeight = "700";
      validateCSSFont(cssFontInfo);
      expect(cssFontInfo.fontWeight).toEqual("700");

      cssFontInfo.fontWeight = "normal";
      validateCSSFont(cssFontInfo);
      expect(cssFontInfo.fontWeight).toEqual("normal");

      cssFontInfo.fontWeight = 314;
      validateCSSFont(cssFontInfo);
      expect(cssFontInfo.fontWeight).toEqual("400");
    });

    it("Check italic angle", function () {
      const cssFontInfo = {
        fontFamily: "blah",
        fontWeight: 100,
        italicAngle: 10,
      };
      validateCSSFont(cssFontInfo);
      expect(cssFontInfo.italicAngle).toEqual("10");

      cssFontInfo.italicAngle = -123;
      validateCSSFont(cssFontInfo);
      expect(cssFontInfo.italicAngle).toEqual("14");

      cssFontInfo.italicAngle = "91";
      validateCSSFont(cssFontInfo);
      expect(cssFontInfo.italicAngle).toEqual("14");

      cssFontInfo.italicAngle = 2.718;
      validateCSSFont(cssFontInfo);
      expect(cssFontInfo.italicAngle).toEqual("2.718");
    });
  });

  describe("isAscii", function () {
    it("handles ascii/non-ascii strings", function () {
      expect(isAscii("hello world")).toEqual(true);
      expect(isAscii("こんにちは世界の")).toEqual(false);
      expect(isAscii("hello world in Japanese is こんにちは世界の")).toEqual(
        false
      );
    });
  });

  describe("stringToUTF16HexString", function () {
    it("should encode a string in UTF16 hexadecimal format", function () {
      expect(stringToUTF16HexString("hello world")).toEqual(
        "00680065006c006c006f00200077006f0072006c0064"
      );

      expect(stringToUTF16HexString("こんにちは世界の")).toEqual(
        "30533093306b3061306f4e16754c306e"
      );
    });
  });

  describe("stringToUTF16String", function () {
    it("should encode a string in UTF16", function () {
      expect(stringToUTF16String("hello world")).toEqual(
        "\0h\0e\0l\0l\0o\0 \0w\0o\0r\0l\0d"
      );

      expect(stringToUTF16String("こんにちは世界の")).toEqual(
        "\x30\x53\x30\x93\x30\x6b\x30\x61\x30\x6f\x4e\x16\x75\x4c\x30\x6e"
      );
    });

    it("should encode a string in UTF16BE with a BOM", function () {
      expect(
        stringToUTF16String("hello world", /* bigEndian = */ true)
      ).toEqual("\xfe\xff\0h\0e\0l\0l\0o\0 \0w\0o\0r\0l\0d");

      expect(
        stringToUTF16String("こんにちは世界の", /* bigEndian = */ true)
      ).toEqual(
        "\xfe\xff\x30\x53\x30\x93\x30\x6b\x30\x61\x30\x6f\x4e\x16\x75\x4c\x30\x6e"
      );
    });
  });

  describe("getSizeInBytes", function () {
    it("should get the size in bytes to use to represent a positive integer", function () {
      expect(getSizeInBytes(0)).toEqual(0);
      for (let i = 1; i <= 0xff; i++) {
        expect(getSizeInBytes(i)).toEqual(1);
      }

      for (let i = 0x100; i <= 0xffff; i += 0x100) {
        expect(getSizeInBytes(i)).toEqual(2);
      }

      for (let i = 0x10000; i <= 0xffffff; i += 0x10000) {
        expect(getSizeInBytes(i)).toEqual(3);
      }
    });
  });
});