diff --git a/UBigInt.pas b/UBigInt.pas
index 56e48f9..a49ea16 100644
--- a/UBigInt.pas
+++ b/UBigInt.pas
@@ -35,6 +35,8 @@ type
     FDigits: TDigits;
     FIsNegative: Boolean;
 
+    function GetSign: Integer;
+
     // Copies consecutive digits from this BigInt to create a new one. The result will be positive. Leading zeros are
     // removed from the result, but AIndex + ACount must not exceed the number of digits of this BigInt.
     // AIndex is the first (least significant) digit to be taken. The digit with this index will become the 0th digit of
@@ -66,11 +68,19 @@ type
     //   Sign * (Abs(a) * Abs(b))
     // where Sign is 1 for ReturnNegative = False and -1 otherwise.
     class function MultiplyAbsoluteValues(constref AA, AB: TBigInt; const AReturnNegative: Boolean): TBigInt; static;
+
+    class function FromHexOrBinString(const AValue: string; const AFromBase: Integer): TBigInt; static;
+    class function ConvertDigitBlock(const AValue: string; var AStartIndex: Integer; const ACharBlockSize, AFromBase:
+      Integer): Cardinal;
   public
     property IsNegative: Boolean read FIsNegative;
+    property Sign: Integer read GetSign;
     class property Zero: TBigInt read GetZero;
     function CompareTo(constref AOther: TBigInt): Integer;
+    function TryToInt64(out AOutput: Int64): Boolean;
     class function FromInt64(const AValue: Int64): TBigInt; static;
+    class function FromHexadecimalString(const AValue: string): TBigInt; static;
+    class function FromBinaryString(const AValue: string): TBigInt; static;
   end;
 
   { Operators }
@@ -83,6 +93,10 @@ type
   operator shl (const A: TBigInt; const B: Integer): TBigInt;
   operator = (const A, B: TBigInt): Boolean;
   operator <> (const A, B: TBigInt): Boolean;
+  operator < (const A, B: TBigInt): Boolean;
+  operator <= (const A, B: TBigInt): Boolean;
+  operator > (const A, B: TBigInt): Boolean;
+  operator >= (const A, B: TBigInt): Boolean;
 
 implementation
 
@@ -98,6 +112,16 @@ const
 
 { TBigInt }
 
+function TBigInt.GetSign: Integer;
+begin
+  if FIsNegative then
+    Result := -1
+  else if (Length(FDigits) > 1) or (FDigits[0] <> 0) then
+    Result := 1
+  else
+    Result := 0;
+end;
+
 function TBigInt.GetSegment(const AIndex, ACount: Integer): TBigInt;
 var
   trimmedCount: Integer;
@@ -105,8 +129,7 @@ begin
   trimmedCount := ACount;
   while (trimmedCount > 1) and (FDigits[AIndex + trimmedCount - 1] = 0) do
     Dec(trimmedCount);
-  SetLength(Result.FDigits, trimmedCount);
-  Move(FDigits[AIndex], Result.FDigits[0], CDigitSize * trimmedCount);
+  Result.FDigits := Copy(FDigits, AIndex, trimmedCount);
   Result.FIsNegative := False;
 end;
 
@@ -138,7 +161,7 @@ end;
 
 class function TBigInt.AddAbsoluteValues(constref AA, AB: TBigInt; const AReturnNegative: Boolean): TBigInt;
 var
-  i, lenA, lenB, len, shorter: Integer;
+  i, j, lenA, lenB, len, shorter: Integer;
   carry: Cardinal;
 begin
   lenA := Length(AA.FDigits);
@@ -185,9 +208,11 @@ begin
   // carry-overs. This avoids additional tests for finding the shorter digit array.
   if (i < lenA) or (i < lenB) then
     if lenA >= lenB then
-      Move(AA.FDigits[i], Result.FDigits[i], CDigitSize * (len - i))
+      for j := i to len - 1 do
+        Result.FDigits[j] := AA.FDigits[j]
     else
-      Move(AB.FDigits[i], Result.FDigits[i], CDigitSize * (len - i));
+      for j := i to len - 1 do
+        Result.FDigits[j] := AB.FDigits[j];
 
   // Applies the remaining carry-overs until the end of the prepared result digit array.
   while (carry > 0) and (i < len) do
@@ -212,7 +237,7 @@ class function TBigInt.SubtractAbsoluteValues(constref AA, AB: TBigInt; const AR
 var
   a, b: TBigInt;
   carry: Cardinal;
-  i, lastNonZeroDigitIndex, len: Integer;
+  i, j, lastNonZeroDigitIndex, len: Integer;
 begin
   // Establishes the operand order, such that Abs(a) is not less than Abs(b).
   if (AA.CompareToAbsoluteValues(AB) >= 0) then
@@ -277,7 +302,8 @@ begin
   // Copies the missing unchanged digits from the longer operand to the result, if any. If there are none, then no trim
   // needs to occur because the most significant digit is not zero.
   if i < len then
-    Move(a.FDigits[i], Result.FDigits[i], CDigitSize * (len - i))
+    for j := i to len - 1 do
+      Result.FDigits[j] := a.FDigits[j]
   else if (lastNonZeroDigitIndex + 1 < len) then
     // Trims leading zeros from the digits array.
     Delete(Result.FDigits, lastNonZeroDigitIndex + 1, len - lastNonZeroDigitIndex - 1);
@@ -362,6 +388,70 @@ begin
   end;
 end;
 
+class function TBigInt.FromHexOrBinString(const AValue: string; const AFromBase: Integer): TBigInt;
+var
+  charBlockSize, offset, i, j, k, remainder: Integer;
+  d: Cardinal;
+begin
+  // 2 ^ (32 / charBlockSize) = AFromBase
+  case AFromBase of
+    2: charBlockSize := 32;
+    16: charBlockSize := 8;
+  end;
+
+  if AValue[1] = '-' then
+  begin
+    offset := 2;
+    Result.FIsNegative := True;
+  end
+  else begin
+    offset := 1;
+    Result.FIsNegative := False;
+  end;
+
+  // Calculates the first (most significant) digit d of the result.
+  DivMod(AValue.Length - offset + 1, charBlockSize, i, remainder);
+  k := offset;
+  d := 0;
+  // Checks the first block of chars that is not a full block.
+  if remainder > 0 then
+    d := ConvertDigitBlock(AValue, k, remainder, AFromBase);
+  // Checks full blocks of chars for first digit.
+  while (d = 0) and (i > 0) do
+  begin
+    Dec(i);
+    d := ConvertDigitBlock(AValue, k, charBlockSize, AFromBase);
+  end;
+
+  // Checks for zero.
+  if (d = 0) and (i = 0) then
+    Result := Zero
+  else begin
+    // Initializes the array of digits.
+    SetLength(Result.FDigits, i + 1);
+    Result.FDigits[i] := d;
+
+    // Calculates the other digits.
+    for j := i - 1 downto 0 do
+      Result.FDigits[j] := ConvertDigitBlock(AValue, k, charBlockSize, AFromBase);
+  end;
+end;
+
+class function TBigInt.ConvertDigitBlock(const AValue: string; var AStartIndex: Integer; const ACharBlockSize,
+  AFromBase: Integer): Cardinal;
+var
+  part: string;
+begin
+  part := Copy(AValue, AStartIndex, ACharBlockSize);
+  Inc(AStartIndex, ACharBlockSize);
+  case AFromBase of
+    2: part := '%' + part;
+    8: part := '&' + part;
+    16: part := '$' + part;
+  end;
+  Result := StrToDWord(part);
+end;
+
 function TBigInt.CompareTo(constref AOther: TBigInt): Integer;
 begin
   if FIsNegative = AOther.FIsNegative then
@@ -372,6 +462,35 @@ begin
     Result := -Result;
 end;
 
+function TBigInt.TryToInt64(out AOutput: Int64): Boolean;
+begin
+  AOutput := 0;
+  Result := False;
+  case Length(FDigits) of
+    0: Result := True;
+    1: begin
+      AOutput := FDigits[0];
+      if FIsNegative then
+        AOutput := -AOutput;
+      Result := True;
+    end;
+    2: begin
+      if FDigits[1] <= Integer.MaxValue then
+      begin
+        AOutput := FDigits[1] * CBase + FDigits[0];
+        if FIsNegative then
+          AOutput := -AOutput;
+        Result := True;
+      end
+      else if (FDigits[1] = Integer.MaxValue + 1) and (FDigits[0] = 0) and FIsNegative then
+      begin
+        AOutput := Int64.MinValue;
+        Result := True;
+      end;
+    end;
+  end;
+end;
+
 class function TBigInt.FromInt64(const AValue: Int64): TBigInt;
 var
   absVal: Int64;
@@ -391,6 +510,16 @@ begin
   end;
 end;
 
+class function TBigInt.FromHexadecimalString(const AValue: string): TBigInt;
+begin
+  Result := FromHexOrBinString(AValue, 16);
+end;
+
+class function TBigInt.FromBinaryString(const AValue: string): TBigInt;
+begin
+  Result := FromHexOrBinString(AValue, 2);
+end;
+
 { Operators }
 
 operator := (const A: Int64): TBigInt;
@@ -403,9 +532,13 @@ var
   len: Integer;
 begin
   len := Length(A.FDigits);
-  SetLength(Result.FDigits, len);
-  Move(A.FDigits[0], Result.FDigits[0], len);
-  Result.FIsNegative := not A.FIsNegative;
+  if (len > 1) or (A.FDigits[0] > 0) then
+  begin
+    Result.FDigits := Copy(A.FDigits, 0, len);
+    Result.FIsNegative := not A.FIsNegative;
+  end
+  else
+    Result := TBigInt.Zero;
 end;
 
 operator + (const A, B: TBigInt): TBigInt;
@@ -475,7 +608,10 @@ begin
       // Performs full digit shifts by copy if there are no bit shifts.
       len := Length(A.FDigits);
       SetLength(Result.FDigits, len + digitShifts);
-      Move(A.FDigits[0], Result.FDigits[digitShifts], CDigitSize * len);
+      for i := 0 to digitShifts - 1 do
+        Result.FDigits[i] := 0;
+      for i := 0 to len - 1 do
+        Result.FDigits[i + digitShifts] := A.FDigits[i];
     end;
 
     Result.FIsNegative := A.IsNegative;
@@ -492,5 +628,25 @@ begin
   Result := A.CompareTo(B) <> 0;
 end;
 
+operator < (const A, B: TBigInt): Boolean;
+begin
+  Result := A.CompareTo(B) < 0;
+end;
+
+operator <= (const A, B: TBigInt): Boolean;
+begin
+  Result := A.CompareTo(B) <= 0;
+end;
+
+operator > (const A, B: TBigInt): Boolean;
+begin
+  Result := A.CompareTo(B) > 0;
+end;
+
+operator >= (const A, B: TBigInt): Boolean;
+begin
+  Result := A.CompareTo(B) >= 0;
+end;
+
 end.
 
diff --git a/tests/AdventOfCodeFPCUnit.lpi b/tests/AdventOfCodeFPCUnit.lpi
index 6d98efa..1d0b455 100644
--- a/tests/AdventOfCodeFPCUnit.lpi
+++ b/tests/AdventOfCodeFPCUnit.lpi
@@ -144,10 +144,18 @@
         
         
       
+      
+        
+        
+      
       
         
         
       
+      
+        
+        
+      
     
   
   
diff --git a/tests/AdventOfCodeFPCUnit.lpr b/tests/AdventOfCodeFPCUnit.lpr
index eddfbea..27320a1 100644
--- a/tests/AdventOfCodeFPCUnit.lpr
+++ b/tests/AdventOfCodeFPCUnit.lpr
@@ -9,7 +9,7 @@ uses
   UHotSpringsTestCases, UPointOfIncidenceTestCases, UParabolicReflectorDishTestCases, ULensLibraryTestCases,
   UFloorWillBeLavaTestCases, UClumsyCrucibleTestCases, ULavaductLagoonTestCases, UAplentyTestCases,
   UPulsePropagationTestCases, UStepCounterTestCases, USandSlabsTestCases, ULongWalkTestCases,
-  UNeverTellMeTheOddsTestCases, UPolynomialTestCases, UPolynomialRootsTestCases;
+  UNeverTellMeTheOddsTestCases, UBigIntTestCases, UPolynomialTestCases, UPolynomialRootsTestCases;
 
 {$R *.res}
 
diff --git a/tests/UBigIntTestCases.pas b/tests/UBigIntTestCases.pas
new file mode 100644
index 0000000..4cba54d
--- /dev/null
+++ b/tests/UBigIntTestCases.pas
@@ -0,0 +1,917 @@
+{
+  Solutions to the Advent Of Code.
+  Copyright (C) 2022-2024  Stefan Müller
+
+  This program is free software: you can redistribute it and/or modify it under
+  the terms of the GNU General Public License as published by the Free Software
+  Foundation, either version 3 of the License, or (at your option) any later
+  version.
+
+  This program is distributed in the hope that it will be useful, but WITHOUT
+  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+  FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License along with
+  this program.  If not, see .
+}
+
+unit UBigIntTestCases;
+
+{$mode ObjFPC}{$H+}
+
+interface
+
+uses
+  Classes, SysUtils, fpcunit, testregistry, UBigInt;
+
+type
+  // TODO: TBigIntAbsTestCase
+  // TODO: TBigIntFromDecTestCase
+  //   TestCase('80091110002223289436355210101231765016693209176113648', 10, '80091110002223289436355210101231765016693209176113648');
+  //   TestCase('-3201281944789146858325672846129872035678639439423746384198412894', 10, '-3201281944789146858325672846129872035678639439423746384198412894');
+  //   TestCase('000000000000000000000000000000000000000080091', 10, '80091');
+  //   TestCase('0000000000000000000000000000000000000000000000', 10, '0');
+  //   TestCase('-000000000000000000000000000000004687616873215464763146843215486643215', 10, '-4687616873215464763146843215486643215');
+  //   TestTryFromDec
+  // TODO: TBigIntFromOctTestCase
+  //   OctValue, 8, DecValue:
+  //   TestCase('3132521', 8, '832849');
+  //   TestCase('772350021110002226514', 8, '9123449598017875276');
+  //   TestCase('-247515726712721', 8, '-11520970560977');
+  //   TestCase('000000000000000000000000000000000000000072', 8, '58');
+  //   TestCase('000000000000000000000000000000000000000000000000000000000', 8, '0');
+  //   OctValue, HexValue:
+  //   TestCase('7440737076307076026772', '3C83BE3E638F82DFA');
+  //   TestCase('1336625076203401614325664', '16F6547C8380E31ABB4');
+  //   TestCase('3254410316166274457257121050201413373225', '6AC84338ECBC97ABCA22840C2DF695');
+  //   TestCase('1441330072562106272767270117307274151276215', '642D81D5C88CBAFBAE09EC75E1A57C8D');
+  //   TestCase('3533665174054677131163436413756431236774257271133', '3ADED4F82CDF964E71E85FBA329EFE2BD725B');
+  //   TestCase('57346415317074055631627141161054073014006076155710653', '5EE686B3C782DCCE5CC271160EC18061F1B791AB');
+  //   TestCase('000000000000000000000000000000245745251354033134', 8, '5838773085550172');
+  //   TestTryFromOct
+  // TODO: TBigIntUnaryPlusTestCase
+  // TODO: TBigIntBitwiseLogicalTestCase
+  // TODO: TBigIntComplementTestCase
+  // TODO: TBigIntConversionTestCase
+  // TODO: TBigIntIncrementDecrementTestCase
+  // TODO: TBigIntQuotientTestCase
+  // TODO: TBigIntShiftRightTestCase
+
+  { TBigIntSignTestCase }
+
+  TBigIntSignTestCase = class(TTestCase)
+  private
+    procedure Test(const AHexValue: string; const AExpectedSign: Integer);
+  published
+    procedure TestZero;
+    procedure TestShortPositive;
+    procedure TestShortNegative;
+    procedure TestLongPositive;
+    procedure TestLongNegative;
+  end;
+
+  { TBigIntFromInt64TestCase }
+
+  TBigIntFromInt64TestCase = class(TTestCase)
+  private
+    procedure Test(const AValue: Int64);
+  published
+    procedure TestShortPositive;
+    procedure TestShortNegative;
+    procedure TestLongPositive;
+    procedure TestLongNegative;
+    procedure TestZero;
+  end;
+
+  { TBigIntFromHexTestCase }
+
+  TBigIntFromHexTestCase = class(TTestCase)
+  private
+    procedure TestShort(const AHexValue: string; const ADecValue: Int64);
+  published
+    procedure TestPositive;
+    procedure TestNegative;
+    procedure TestZero;
+    procedure TestLeadingZeros;
+    // TODO: TestTryFromHex
+  end;
+
+  { TBigIntFromBinTestCase }
+
+  TBigIntFromBinTestCase = class(TTestCase)
+  private
+    procedure TestShort(const ABinValue: string; const ADecValue: Int64);
+  published
+    procedure TestPositive;
+    procedure TestNegative;
+    procedure TestLeadingZeros;
+    // TODO: TestTryFromBin
+  end;
+
+  { TBigIntUnaryMinusTestCase }
+
+  TBigIntUnaryMinusTestCase = class(TTestCase)
+  private
+    procedure Test(const AValue: Int64);
+    procedure TestTwice(const AValue: Int64);
+  published
+    procedure TestZero;
+    procedure TestPositive;
+    procedure TestNegative;
+    procedure TestPositiveTwice;
+    procedure TestNegativeTwice;
+  end;
+
+  { TBigIntSumTestCase }
+
+  TBigIntSumTestCase = class(TTestCase)
+  private
+    procedure Test(const AHexValueLeft, AHexValueRight, AHexValueSum: string);
+  published
+    procedure TestShort;
+    procedure TestPositivePlusPositive;
+    procedure TestNegativePlusNegative;
+    procedure TestLargePositivePlusSmallNegative;
+    procedure TestSmallPositivePlusLargeNegative;
+    procedure TestLargeNegativePlusSmallPositive;
+    procedure TestSmallNegativePlusLargePositive;
+    procedure TestZeroPlusPositive;
+    procedure TestPositivePlusZero;
+    procedure TestZero;
+    procedure TestSumShorterLeft;
+    procedure TestSumShorterRight;
+    procedure TestSumEndsInCarry;
+    procedure TestSumEndsInCarryNewDigit;
+    procedure TestSumMultiCarry;
+  end;
+
+  { TBigIntDifferenceTestCase }
+
+  TBigIntDifferenceTestCase = class(TTestCase)
+  private
+    procedure Test(const AHexValueMinuend, AHexValueSubtrahend, AHexValueDifference: string);
+  published
+    procedure TestShort;
+    procedure TestLargePositiveMinusSmallPositive;
+    procedure TestSmallPositiveMinusLargePositive;
+    procedure TestLargeNegativeMinusSmallNegative;
+    procedure TestSmallNegativeMinusLargeNegative;
+    procedure TestNegativeMinusPositive;
+    procedure TestPositiveMinusNegative;
+    procedure TestLargeOperands;
+    procedure TestPositiveMinusZero;
+    procedure TestZeroMinusPositive;
+    procedure TestZero;
+    procedure TestDifferenceShorterLeft;
+    procedure TestDifferenceShorterRight;
+    procedure TestDifferenceEndsInCarry;
+    procedure TestDifferenceEndsInCarryLosingDigit;
+    procedure TestDifferenceMultiCarry;
+  end;
+
+  { TBigIntProductTestCase }
+
+  TBigIntProductTestCase = class(TTestCase)
+  private
+    procedure Test(const AHexValueLeft, AHexValueRight, AHexValueProduct: string);
+  published
+    procedure TestShort;
+    procedure TestLongPositiveTimesPositive;
+    procedure TestLongPositiveTimesNegative;
+    procedure TestLongNegativeTimesPositive;
+    procedure TestLongNegativeTimesNegative;
+    procedure TestZeroTimesPositive;
+    procedure TestZeroTimesNegative;
+    procedure TestZero;
+  end;
+
+  { TBigIntShiftLeftTestCase }
+
+  TBigIntShiftLeftTestCase = class(TTestCase)
+  private
+    procedure Test(const AHexValueOperand: string; const AShift: Integer; const AHexValueResult: string);
+  published
+    procedure TestShort;
+    procedure TestShortWithCarry;
+    procedure TestLongWithCarry;
+    procedure TestLongWithMultiDigitCarry;
+    procedure TestWithAlignedDigits;
+    procedure TestZero;
+  end;
+
+  { TBigIntEqualityTestCase }
+
+  TBigIntEqualityTestCase = class(TTestCase)
+  private
+    procedure TestEqual(const AValue: Int64);
+    procedure TestEqualHex(const AHexValue: string);
+    procedure TestNotEqualHex(const AHexValueLeft, AHexValueRight: string);
+  published
+    procedure TestShortEqual;
+    procedure TestLongEqual;
+    procedure TestZeroEqual;
+    procedure TestShortNotEqual;
+    procedure TestLongNotEqualSign;
+    procedure TestZeroNotEqual;
+  end;
+
+  { TBigIntComparisonTestCase }
+
+  TBigIntComparisonTestCase = class(TTestCase)
+  private
+    procedure TestLessThan(const AHexValueLeft, AHexValueRight: string);
+    procedure TestGreaterThan(const AHexValueLeft, AHexValueRight: string);
+    procedure TestEqual(const AHexValue: string);
+  published
+    procedure TestLessSameLength;
+    procedure TestLessShorterLeft;
+    procedure TestLessNegativeShorterRight;
+    procedure TestGreaterSameLength;
+    procedure TestGreaterShorterRight;
+    procedure TestGreaterNegativeShorterLeft;
+    procedure TestEqualPositive;
+    procedure TestEqualNegative;
+    procedure TestEqualZero;
+  end;
+
+implementation
+
+{ TBigIntSignTestCase }
+
+procedure TBigIntSignTestCase.Test(const AHexValue: string; const AExpectedSign: Integer);
+var
+  a: TBigInt;
+begin
+  a := TBigInt.FromHexadecimalString(AHexValue);
+  AssertEquals(AExpectedSign, a.Sign);
+end;
+
+procedure TBigIntSignTestCase.TestZero;
+begin
+  Test('0', 0);
+end;
+
+procedure TBigIntSignTestCase.TestShortPositive;
+begin
+  Test('36A', 1);
+end;
+
+procedure TBigIntSignTestCase.TestShortNegative;
+begin
+  Test('-29B7', -1);
+end;
+
+procedure TBigIntSignTestCase.TestLongPositive;
+begin
+  Test('1240168AB09ABDF8283B77124', 1);
+end;
+
+procedure TBigIntSignTestCase.TestLongNegative;
+begin
+  Test('-192648F1305DD04757A24C873F29F60B6184B5', -1);
+end;
+
+{ TBigIntFromInt64TestCase }
+
+procedure TBigIntFromInt64TestCase.Test(const AValue: Int64);
+var
+  a: TBigInt;
+  act: Int64;
+begin
+  a := TBigInt.FromInt64(AValue);
+  AssertTrue('BigInt from ''' + IntToStr(AValue) + ''' could not be converted back to an Int64 value.',
+    a.TryToInt64(act));
+  AssertEquals('BigInt from ''' + IntToStr(AValue) + ''' converted back to Int64 was not equal to initial value.',
+    AValue, act);
+end;
+
+procedure TBigIntFromInt64TestCase.TestShortPositive;
+begin
+  Test(17);
+  Test(4864321);
+  Test(Cardinal.MaxValue);
+end;
+
+procedure TBigIntFromInt64TestCase.TestShortNegative;
+begin
+  Test(-54876);
+  Test(Integer.MinValue);
+end;
+
+procedure TBigIntFromInt64TestCase.TestLongPositive;
+begin
+  Test(5800754643214654);
+  Test(Int64.MaxValue);
+end;
+
+procedure TBigIntFromInt64TestCase.TestLongNegative;
+begin
+  Test(-94136445555883);
+  Test(Int64.MinValue);
+end;
+
+procedure TBigIntFromInt64TestCase.TestZero;
+begin
+  Test(0);
+end;
+
+{ TBigIntFromHexTestCase }
+
+procedure TBigIntFromHexTestCase.TestShort(const AHexValue: string; const ADecValue: Int64);
+var
+  a, b: TBigInt;
+begin
+  a := TBigInt.FromHexadecimalString(AHexValue);
+  b := TBigInt.FromInt64(ADecValue);
+  AssertTrue('BigInt from hexadecimal string ''' + AHexValue + ''' was not equal to ''' + IntToStr(ADecValue) + '''.',
+    a = b);
+end;
+
+procedure TBigIntFromHexTestCase.TestPositive;
+begin
+  TestShort('91', 145);
+  TestShort('800E111000222', 2252766466540066);
+  TestShort('DE0B227802AB233', 999995000000000563);
+  TestShort('19C0048155000', 453000000000000);
+  TestShort('3B9ACA00', 1000000000);
+end;
+
+procedure TBigIntFromHexTestCase.TestNegative;
+begin
+  TestShort('-47', -71);
+  TestShort('-800E111000222', -2252766466540066);
+  TestShort('-4512FF3', -72429555);
+end;
+
+procedure TBigIntFromHexTestCase.TestZero;
+begin
+  TestShort('0', 0);
+  TestShort('-0', 0);
+end;
+
+procedure TBigIntFromHexTestCase.TestLeadingZeros;
+begin
+  TestShort('000000000000000000000000000000004B', 75);
+  TestShort('-00000000000000000000000000000000A2', -162);
+  TestShort('00000000000000000000000000000000FF452849DB01', 280672493755137);
+  TestShort('000000000000000000000000000000000000', 0);
+  TestShort('-000000000000000000000000000000000000', 0);
+end;
+
+{ TBigIntFromBinTestCase }
+
+procedure TBigIntFromBinTestCase.TestShort(const ABinValue: string; const ADecValue: Int64);
+var
+  a, b: TBigInt;
+begin
+  a := TBigInt.FromBinaryString(ABinValue);
+  b := TBigInt.FromInt64(ADecValue);
+  AssertTrue('BigInt from binary string ''' + ABinValue + ''' was not equal to ''' + IntToStr(ADecValue) + '''.',
+    a = b);
+end;
+
+procedure TBigIntFromBinTestCase.TestPositive;
+begin
+  TestShort('110101010101101101010010110000101010100101001001010100110', 120109162101379750);
+end;
+
+procedure TBigIntFromBinTestCase.TestNegative;
+begin
+  TestShort('-11100100111010100111000111100011110000100110110111100101010010', -4123780452057839954);
+end;
+
+procedure TBigIntFromBinTestCase.TestLeadingZeros;
+begin
+  TestShort('0000000000000000000000000000000000000000000000000000000000000000000000111', 7);
+  TestShort('0000000000000000000000000000000000000000000000000000000000000000000000000000000', 0);
+end;
+
+{ TBigIntUnaryMinusTestCase }
+
+procedure TBigIntUnaryMinusTestCase.Test(const AValue: Int64);
+var
+  a, b: TBigInt;
+begin
+  a := TBigInt.FromInt64(AValue);
+  b := TBigInt.FromInt64(-AValue);
+  AssertTrue('Negative BigInt from ''' + IntToStr(AValue) + ''' was not equal to the BigInt from the negative value.',
+    b = -a);
+end;
+
+procedure TBigIntUnaryMinusTestCase.TestTwice(const AValue: Int64);
+var
+  a: TBigInt;
+begin
+  a := TBigInt.FromInt64(AValue);
+  AssertTrue('BigInt from ''' + IntToStr(AValue) + '''was not equal to the double negative of itself.',
+    a = -(-a));
+end;
+
+procedure TBigIntUnaryMinusTestCase.TestZero;
+begin
+  Test(0);
+end;
+
+procedure TBigIntUnaryMinusTestCase.TestPositive;
+begin
+  Test(234972358233);
+end;
+
+procedure TBigIntUnaryMinusTestCase.TestNegative;
+begin
+  Test(-999214927400);
+end;
+
+procedure TBigIntUnaryMinusTestCase.TestPositiveTwice;
+begin
+  TestTwice(8647613456601);
+end;
+
+procedure TBigIntUnaryMinusTestCase.TestNegativeTwice;
+begin
+  TestTwice(-38600421308534);
+end;
+
+{ TBigIntSumTestCase }
+
+procedure TBigIntSumTestCase.Test(const AHexValueLeft, AHexValueRight, AHexValueSum: string);
+var
+  a, b, s: TBigInt;
+begin
+  a := TBigInt.FromHexadecimalString(AHexValueLeft);
+  b := TBigInt.FromHexadecimalString(AHexValueRight);
+  s := TBigInt.FromHexadecimalString(AHexValueSum);
+  AssertTrue('Sum of BigInt from ''' + AHexValueLeft + ''' and from ''' + AHexValueRight
+    + ''' was not equal to the BigInt from ''' + AHexValueSum + '''.',
+    s = a + b);
+end;
+
+procedure TBigIntSumTestCase.TestShort;
+begin
+  Test('5', '7', 'C');
+end;
+
+procedure TBigIntSumTestCase.TestPositivePlusPositive;
+begin
+  Test('7000822000111', '9000911000333', '10001133000444');
+end;
+
+procedure TBigIntSumTestCase.TestNegativePlusNegative;
+begin
+  Test('-129B92A84643D608141', '-4574DBA206951ECFE', '-12E10783E84A6B26E3F');
+end;
+
+procedure TBigIntSumTestCase.TestLargePositivePlusSmallNegative;
+begin
+  Test('87BAD26984', '-8DCB20461', '7EDE206523');
+end;
+
+procedure TBigIntSumTestCase.TestSmallPositivePlusLargeNegative;
+begin
+  Test('A58301E4006', '-9851DA0FD433', '-8DF9A9F1942D');
+end;
+
+procedure TBigIntSumTestCase.TestLargeNegativePlusSmallPositive;
+begin
+  Test('-1FDB60CB5698870', '99CB1E00DE', '-1FDB572EA4B8792');
+end;
+
+procedure TBigIntSumTestCase.TestSmallNegativePlusLargePositive;
+begin
+  Test('-1ED598BBFEC2', '59CD4F02ECB56', '57DFF5772CC94');
+end;
+
+procedure TBigIntSumTestCase.TestZeroPlusPositive;
+begin
+  Test('0', '9BB000911FF5A000333', '9BB000911FF5A000333');
+end;
+
+procedure TBigIntSumTestCase.TestPositivePlusZero;
+begin
+  Test('23009605A16BCBB294A1FD', '0', '23009605A16BCBB294A1FD');
+end;
+
+procedure TBigIntSumTestCase.TestZero;
+begin
+  Test('0', '0', '0');
+end;
+
+procedure TBigIntSumTestCase.TestSumShorterLeft;
+begin
+  Test('3FFFF', '9000911000222', '9000911040221');
+end;
+
+procedure TBigIntSumTestCase.TestSumShorterRight;
+begin
+  Test('9000911000555', '3000EEEE', '900094100F443');
+end;
+
+procedure TBigIntSumTestCase.TestSumEndsInCarry;
+begin
+  Test('4000444000220', 'FFFFFFFF', '400054400021F');
+end;
+
+procedure TBigIntSumTestCase.TestSumEndsInCarryNewDigit;
+begin
+  Test('99990000', '99990055', '133320055');
+end;
+
+procedure TBigIntSumTestCase.TestSumMultiCarry;
+begin
+  Test('FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF', 'FFFFFFFF', '1000000000000000000000000FFFFFFFE');
+end;
+
+{ TBigIntDifferenceTestCase }
+
+procedure TBigIntDifferenceTestCase.Test(const AHexValueMinuend, AHexValueSubtrahend, AHexValueDifference: string);
+var
+  a, b, s: TBigInt;
+begin
+  a := TBigInt.FromHexadecimalString(AHexValueMinuend);
+  b := TBigInt.FromHexadecimalString(AHexValueSubtrahend);
+  s := TBigInt.FromHexadecimalString(AHexValueDifference);
+  AssertTrue('Difference of BigInt from ''' + AHexValueMinuend + ''' and from ''' + AHexValueSubtrahend
+    + ''' was not equal to the BigInt from ''' + AHexValueDifference + '''.',
+    s = a - b);
+end;
+
+procedure TBigIntDifferenceTestCase.TestShort;
+begin
+  Test('230', '6D', '1C3');
+end;
+
+procedure TBigIntDifferenceTestCase.TestLargePositiveMinusSmallPositive;
+begin
+  Test('910AAD86E5002455', '72DE020F932A1', '91037FA6C406F1B4');
+end;
+
+procedure TBigIntDifferenceTestCase.TestSmallPositiveMinusLargePositive;
+begin
+  Test('3127541F4C0AA', '3818CD9FBE652B', '-3506585DC9A481');
+end;
+
+procedure TBigIntDifferenceTestCase.TestLargeNegativeMinusSmallNegative;
+begin
+  Test('-B12BE1E20098', '-148F3137CED396', '13DE0555ECD2FE');
+end;
+
+procedure TBigIntDifferenceTestCase.TestSmallNegativeMinusLargeNegative;
+begin
+  Test('-AF3FF1EC626908C', '-18295', '-AF3FF1EC6250DF7');
+end;
+
+procedure TBigIntDifferenceTestCase.TestNegativeMinusPositive;
+begin
+  Test('-E493506B19', '20508ED255', '-104E3DF3D6E');
+end;
+
+procedure TBigIntDifferenceTestCase.TestPositiveMinusNegative;
+begin
+  Test('114EEC66851AFD98', '-100AA4308C5249FBBFADEB89CD6A7D9CC', '100AA4308C5249FBC0C2DA5035BC2D764');
+end;
+
+procedure TBigIntDifferenceTestCase.TestLargeOperands;
+begin
+  Test('1069FC8EA3D99C39E1C07AA078B77B5CC679CB448563345A878C603D32FB0F8FEFE02AD9574A5EB6',
+    '1069FC8EA3D99C39E1C07AA078B77B5CC679CB448563345A878C603D32FB0F8FEFE023C522B87F8C',
+    '7143491DF2A');
+end;
+
+procedure TBigIntDifferenceTestCase.TestPositiveMinusZero;
+begin
+  Test('8ABB000911FF5A000333', '0', '8ABB000911FF5A000333');
+end;
+
+procedure TBigIntDifferenceTestCase.TestZeroMinusPositive;
+begin
+  Test('0', '243961982DDD64F81B2', '-243961982DDD64F81B2');
+end;
+
+procedure TBigIntDifferenceTestCase.TestZero;
+begin
+  Test('0', '0', '0');
+end;
+
+procedure TBigIntDifferenceTestCase.TestDifferenceShorterLeft;
+begin
+  Test('3FFFF', '9000911040221', '-9000911000222');
+end;
+
+procedure TBigIntDifferenceTestCase.TestDifferenceShorterRight;
+begin
+  Test('900094100F443', '3000EEEE', '9000911000555');
+end;
+
+procedure TBigIntDifferenceTestCase.TestDifferenceEndsInCarry;
+begin
+  Test('400054400021F', 'FFFFFFFF', '4000444000220');
+end;
+
+procedure TBigIntDifferenceTestCase.TestDifferenceEndsInCarryLosingDigit;
+begin
+  Test('133320055', '99990000', '99990055');
+end;
+
+procedure TBigIntDifferenceTestCase.TestDifferenceMultiCarry;
+begin
+  Test('1000000000000000000000000FFFFFFFE', 'FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF', 'FFFFFFFF');
+end;
+
+{ TBigIntProductTestCase }
+
+procedure TBigIntProductTestCase.Test(const AHexValueLeft, AHexValueRight, AHexValueProduct: string);
+var
+  a, b, s: TBigInt;
+begin
+  a := TBigInt.FromHexadecimalString(AHexValueLeft);
+  b := TBigInt.FromHexadecimalString(AHexValueRight);
+  s := TBigInt.FromHexadecimalString(AHexValueProduct);
+  AssertTrue('Product of BigInt from ''' + AHexValueLeft + ''' and from ''' + AHexValueRight
+    + ''' was not equal to the BigInt from ''' + AHexValueProduct + '''.',
+    s = a * b);
+end;
+
+procedure TBigIntProductTestCase.TestShort;
+begin
+  Test('9', 'B', '63');
+  Test('29E531A', 'DF5F299', '248E3915103E8A');
+end;
+
+procedure TBigIntProductTestCase.TestLongPositiveTimesPositive;
+begin
+  Test('FFFFFFFF', 'FFFFFFFF', 'FFFFFFFE00000001');
+  Test('4873B23699D07741F1544862221B1966AA84512', '4DE0013', '160A322C656DEB1DD6D721D36E35F2E29B4D2A18192056');
+  Test('74FD3E6988116762', '22DB271AFC4941', 'FEDC8CD51DEE46BE83C283B5E31E2');
+end;
+
+procedure TBigIntProductTestCase.TestLongPositiveTimesNegative;
+begin
+  Test('23401834190D12FF3210F0B0129123AA', '-A4C0530234', '-16AF8B019CA1436BBFD1F1FB08494FFC9EF7E09288');
+end;
+
+procedure TBigIntProductTestCase.TestLongNegativeTimesPositive;
+begin
+  Test('-3ACB78882923810', 'F490B8022A4BCBFF34E01', '-382B2B9851BC93CB0308B502C3B036D71810');
+end;
+
+procedure TBigIntProductTestCase.TestLongNegativeTimesNegative;
+begin
+  Test('-554923FB201', '-9834FDC032', '32B514C1BA1E774EE8432');
+end;
+
+procedure TBigIntProductTestCase.TestZeroTimesPositive;
+begin
+  Test('0', '1AF5D0039B888AC00F299', '0');
+end;
+
+procedure TBigIntProductTestCase.TestZeroTimesNegative;
+begin
+  Test('0', '-1AF5D0039B888AC00F299', '0');
+end;
+
+procedure TBigIntProductTestCase.TestZero;
+begin
+  Test('0', '0', '0');
+end;
+
+{ TBigIntShiftLeftTestCase }
+
+procedure TBigIntShiftLeftTestCase.Test(const AHexValueOperand: string; const AShift: Integer; const AHexValueResult: string);
+var
+  a, s: TBigInt;
+begin
+  a := TBigInt.FromHexadecimalString(AHexValueOperand);
+  s := TBigInt.FromHexadecimalString(AHexValueResult);
+  AssertTrue('BigInt from hexadecimal string ''' + AHexValueOperand + ''' shifted left by ''' + IntToStr(AShift)
+    + ''' was not equal to BigInt from hexadecimal string ''' + AHexValueResult + '''.',
+    s = (a << AShift));
+end;
+
+procedure TBigIntShiftLeftTestCase.TestShort;
+begin
+  // BIN 101
+  // BIN 101000
+  Test('5', 3, '28');
+end;
+
+procedure TBigIntShiftLeftTestCase.TestShortWithCarry;
+begin
+  // BIN 1110 1101 0111 0001 1010 1010
+  // BIN 1 1101 1010 1110 0011 0101 0100 0000 0000 0000
+  Test('ED71AA', 13, '1DAE354000');
+end;
+
+procedure TBigIntShiftLeftTestCase.TestLongWithCarry;
+begin
+  // BIN 1 0011 0000 1011 0010 0011 1110 0100 1100 1111 1001 0101 0100 0100 0101
+  // BIN 10 0110 0001 0110 0100 0111 1100 1001 1001 1111 0010 1010 1000 1000 1010 0000 0000
+  Test('130B23E4CF95445', 9, '261647C99F2A88A00');
+end;
+
+procedure TBigIntShiftLeftTestCase.TestLongWithMultiDigitCarry;
+begin
+  Test('C99F12A735A3B83901BF92011', 140, 'C99F12A735A3B83901BF9201100000000000000000000000000000000000');
+end;
+
+procedure TBigIntShiftLeftTestCase.TestWithAlignedDigits;
+begin
+  // Shifts the left operand by a multiple of the length of full TBigInt digits, so the digits will be shifted, but not
+  // changed.
+  Test('10F0F39C5E', 32 * 4, '10F0F39C5E00000000000000000000000000000000');
+end;
+
+procedure TBigIntShiftLeftTestCase.TestZero;
+begin
+  Test('0', 119, '0');
+end;
+
+{ TBigIntEqualityTestCase }
+
+procedure TBigIntEqualityTestCase.TestEqual(const AValue: Int64);
+var
+  a, b: TBigInt;
+begin
+  a := TBigInt.FromInt64(AValue);
+  b := TBigInt.FromInt64(AValue);
+  AssertTrue('Two BigInt from ''' + IntToStr(AValue) + ''' were not equal.', a = b);
+  AssertFalse('Two BigInt from ''' + IntToStr(AValue) + ''' were un-equal.', a <> b);
+end;
+
+procedure TBigIntEqualityTestCase.TestEqualHex(const AHexValue: string);
+var
+  a, b: TBigInt;
+begin
+  a := TBigInt.FromHexadecimalString(AHexValue);
+  b := TBigInt.FromHexadecimalString(AHexValue);
+  AssertTrue('Two BigInt from ''' + AHexValue + ''' were not equal.', a = b);
+  AssertFalse('Two BigInt from ''' + AHexValue + ''' were un-equal.', a <> b);
+end;
+
+procedure TBigIntEqualityTestCase.TestNotEqualHex(const AHexValueLeft, AHexValueRight: string);
+var
+  a, b: TBigInt;
+begin
+  a := TBigInt.FromHexadecimalString(AHexValueLeft);
+  b := TBigInt.FromHexadecimalString(AHexValueRight);
+  AssertTrue('BigInt from ''' + AHexValueLeft + ''' and from ''' + AHexValueRight + ''' were not un-equal.',
+    a <> b);
+  AssertFalse('BigInt from ''' + AHexValueLeft + ''' and from ''' + AHexValueRight + ''' were equal.',
+    a = b);
+end;
+
+procedure TBigIntEqualityTestCase.TestShortEqual;
+begin
+  TestEqual(14);
+  TestEqualHex('8000111000111');
+end;
+
+procedure TBigIntEqualityTestCase.TestLongEqual;
+begin
+  TestEqualHex('5AB60FF292A014BF1DD0A');
+end;
+
+procedure TBigIntEqualityTestCase.TestZeroEqual;
+begin
+  TestEqual(0);
+end;
+
+procedure TBigIntEqualityTestCase.TestShortNotEqual;
+begin
+  TestNotEqualHex('9FF99920', '100');
+  TestNotEqualHex('20001110002111', '70001110007111');
+end;
+
+procedure TBigIntEqualityTestCase.TestLongNotEqualSign;
+begin
+  TestNotEqualHex('48843AB320FF0041123A', '-48843AB320FF0041123A');
+  TestNotEqualHex('-B13F79D842A30957DD09523667', 'B13F79D842A30957DD09523667');
+end;
+
+procedure TBigIntEqualityTestCase.TestZeroNotEqual;
+begin
+  TestNotEqualHex('0', 'F');
+  TestNotEqualHex('568F7', '0');
+end;
+
+{ TBigIntComparisonTestCase }
+
+procedure TBigIntComparisonTestCase.TestLessThan(const AHexValueLeft, AHexValueRight: string);
+var
+  a, b: TBigInt;
+begin
+  a := TBigInt.FromHexadecimalString(AHexValueLeft);
+  b := TBigInt.FromHexadecimalString(AHexValueRight);
+  AssertTrue('BigInt from ''' + AHexValueLeft + ''' was greater than BigInt from ''' + AHexValueRight + '''.',
+    a < b);
+  AssertTrue('BigInt from ''' + AHexValueLeft + ''' was greater or equal than BigInt from ''' + AHexValueRight + '''.',
+    a <= b);
+  AssertFalse('BigInt from ''' + AHexValueLeft + ''' was greater than BigInt from ''' + AHexValueRight + '''.',
+    a > b);
+  AssertFalse('BigInt from ''' + AHexValueLeft + ''' was greater or equal than BigInt from ''' + AHexValueRight + '''.',
+    a >= b);
+end;
+
+procedure TBigIntComparisonTestCase.TestGreaterThan(const AHexValueLeft, AHexValueRight: string);
+var
+  a, b: TBigInt;
+begin
+  a := TBigInt.FromHexadecimalString(AHexValueLeft);
+  b := TBigInt.FromHexadecimalString(AHexValueRight);
+  AssertFalse('BigInt from ''' + AHexValueLeft + ''' was less than BigInt from ''' + AHexValueRight + '''.',
+    a < b);
+  AssertFalse('BigInt from ''' + AHexValueLeft + ''' was less or equal than BigInt from ''' + AHexValueRight + '''.',
+    a <= b);
+  AssertTrue('BigInt from ''' + AHexValueLeft + ''' was less than BigInt from ''' + AHexValueRight + '''.',
+    a > b);
+  AssertTrue('BigInt from ''' + AHexValueLeft + ''' was less or equal than BigInt from ''' + AHexValueRight + '''.',
+    a >= b);
+end;
+
+procedure TBigIntComparisonTestCase.TestEqual(const AHexValue: string);
+var
+  a, b: TBigInt;
+begin
+  a := TBigInt.FromHexadecimalString(AHexValue);
+  b := TBigInt.FromHexadecimalString(AHexValue);
+  AssertFalse('First BigInt from ''' + AHexValue + ''' was less than the second.',
+    a < b);
+  AssertTrue('First BigInt from ''' + AHexValue + ''' was greater than the second.',
+    a <= b);
+  AssertFalse('First BigInt from ''' + AHexValue + ''' was greater than the second.',
+    a > b);
+  AssertTrue('First BigInt from ''' + AHexValue + ''' was less than the second.',
+    a >= b);
+end;
+
+procedure TBigIntComparisonTestCase.TestLessSameLength;
+begin
+  TestLessThan('104234FF2B29100C012', '234867AB261F1003429103C');
+  TestLessThan('-9812FB2964AC7632865238BBD3', '294625DF51B2A842582244C18163490');
+  TestLessThan('-12834653A2856DF8', '-A946C2BF89401B8');
+  TestLessThan('-2F846', '0');
+  TestLessThan('0', 'FF67B');
+end;
+
+procedure TBigIntComparisonTestCase.TestLessShorterLeft;
+begin
+  TestLessThan('34FF2B29100C012', '234867AB261F1003429103C');
+  TestLessThan('0', 'BFF008112BA00012');
+end;
+
+procedure TBigIntComparisonTestCase.TestLessNegativeShorterRight;
+begin
+  TestLessThan('-9B72844AC', '1F3486B');
+  TestLessThan('-BB884F022111190', '0');
+end;
+
+procedure TBigIntComparisonTestCase.TestGreaterSameLength;
+begin
+  TestGreaterThan('B042104234FF2B29100C012', '23867AB261F1003429103C');
+  TestGreaterThan('1294B77', '-611F3B93');
+  TestGreaterThan('-782163498326593562D548AAF715B4DC9143E42C68F39A29BB2', '-FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF');
+  TestGreaterThan('783BDA0', '0');
+  TestGreaterThan('0', '-99B6D');
+end;
+
+procedure TBigIntComparisonTestCase.TestGreaterShorterRight;
+begin
+  TestGreaterThan('102343234423FF67278B11ADD345F6BB21232C9129100C012', '234867AB261F1003429103C');
+  TestGreaterThan('249D00F63BBAA8668B23', '0');
+end;
+
+procedure TBigIntComparisonTestCase.TestGreaterNegativeShorterLeft;
+begin
+  TestGreaterThan('81F2A7B78B812', '-23490D7F19F247F91A365B1893BB701');
+  TestGreaterThan('0', '-80F88242B34127');
+end;
+
+procedure TBigIntComparisonTestCase.TestEqualPositive;
+begin
+  TestEqual('A44B80191059CA123318921A219BB');
+end;
+
+procedure TBigIntComparisonTestCase.TestEqualNegative;
+begin
+  TestEqual('-28912798DD1246DAC9FB4269908012D496896812FF3A8D071B32');
+end;
+
+procedure TBigIntComparisonTestCase.TestEqualZero;
+begin
+  TestEqual('0');
+end;
+
+initialization
+
+  RegisterTest(TBigIntSignTestCase);
+  RegisterTest(TBigIntFromInt64TestCase);
+  RegisterTest(TBigIntFromHexTestCase);
+  RegisterTest(TBigIntFromBinTestCase);
+  RegisterTest(TBigIntUnaryMinusTestCase);
+  RegisterTest(TBigIntSumTestCase);
+  RegisterTest(TBigIntDifferenceTestCase);
+  RegisterTest(TBigIntProductTestCase);
+  RegisterTest(TBigIntShiftLeftTestCase);
+  RegisterTest(TBigIntEqualityTestCase);
+  RegisterTest(TBigIntComparisonTestCase);
+end.
+