cpp-bignumber/test/biginteger.t.h

//
//  biginteger.t.h
//  bigdecimal
//
//  Created by Sam Jaffe on 6/30/17.
//

#pragma once

#include "biginteger.h"

#include <cxxtest/TestSuite.h>

class biginteger_TestSuite : public CxxTest::TestSuite {
public:
  void testConstructFromStringIsSameValueAsFromInt() {
    using bi = math::biginteger;
    TS_ASSERT_EQUALS(bi("1000000"), bi(1000000));
  }
  
  void testAddPastBounds() {
    math::biginteger bi{999999999ULL};
    TS_ASSERT_EQUALS((bi+1).to_string(), "1000000000");
  }
  
  void testAddReciprocalIsZero() {
    math::biginteger bi{1000};
    TS_ASSERT_EQUALS((bi+(-bi)).to_string(), "0");
  }

  void testAddNegativeLargerGivesNegative() {
    math::biginteger bi{1000};
    TS_ASSERT_EQUALS((bi+(-1001)).to_string(), "-1");
  }

  void testAddNegativeSmallerGivesPositive() {
    math::biginteger bi{1000};
    TS_ASSERT_EQUALS((bi+(-999)).to_string(), "1");
  }
  
  void testSubSelfIsZero() {
    math::biginteger bi{1000};
    TS_ASSERT_EQUALS((bi-bi).to_string(), "0");
  }
  
  void testNegativeMinusNegativeIncreateAbs() {
    math::biginteger bi{-1000};
    TS_ASSERT_EQUALS((bi-100).to_string(), "-1100");
  }
  
  void testSubLargerGivesNegative() {
    math::biginteger bi{1000};
    TS_ASSERT_EQUALS((bi-1001).to_string(), "-1");
  }
  
  void testSubSmallerGivesPositive() {
    math::biginteger bi{1000};
    TS_ASSERT_EQUALS((bi-999).to_string(), "1");
  }

  void testSubUnderflowBorrows() {
    math::biginteger bi{1000000000ULL};
    TS_ASSERT_EQUALS((bi-1).to_string(), "999999999");
  }

  void testMultiplyZeroReturnsZero() {
    auto &ZERO =  math::biginteger::ZERO;
    math::biginteger bi{999999999ULL};
    TS_ASSERT_EQUALS(bi*ZERO, ZERO);
    TS_ASSERT_EQUALS(ZERO*bi, ZERO);
  }
  
  void testMultiplyOneReturnsValue() {
    auto &ONE =  math::biginteger::ONE;
    math::biginteger bi{999999999ULL};
    TS_ASSERT_EQUALS((bi*ONE).to_string(), "999999999");
    TS_ASSERT_EQUALS((ONE*bi).to_string(), "999999999");
  }

  void testMultiplyNegativeOneReturnsInverse() {
    auto &NEGATIVE_ONE =  math::biginteger::NEGATIVE_ONE;
    math::biginteger bi{999999999ULL};
    TS_ASSERT_EQUALS((bi*NEGATIVE_ONE).to_string(), "-999999999");
    TS_ASSERT_EQUALS((NEGATIVE_ONE*bi).to_string(), "-999999999");
  }
  
  void testMultiplyOverflowsIntoNextCell() {
    math::biginteger bi{999999999ULL};
    TS_ASSERT_EQUALS((bi*bi).to_string(), "999999998000000001");
  }
  
  void testMultiplyCarryIntoNextCell() {
    math::biginteger bi{999999999ULL};
    math::biginteger big{bi*bi};
    TS_ASSERT_EQUALS((big*big).to_string(),
                     "999999996000000005999999996000000001");
  }
  
  void testMultiplyNoOverflow() {
    math::biginteger bi{1000};
    TS_ASSERT_EQUALS((bi*bi).to_string(), "1000000");
  }
  
  void testDivideByZeroThrows() {
    auto &ZERO =  math::biginteger::ZERO;
    math::biginteger bi{1000};
    TS_ASSERT_THROWS(bi/ZERO, std::domain_error);
  }
  
  void testDivideByOneReturnsValue() {
    auto &ONE =  math::biginteger::ONE;
    math::biginteger bi{1000};
    TS_ASSERT_EQUALS(bi/ONE, bi);
  }

  void testDivideByNegativeOneReturnsInverse() {
    auto &NEGATIVE_ONE =  math::biginteger::NEGATIVE_ONE;
    math::biginteger bi{1000};
    TS_ASSERT_EQUALS((bi/NEGATIVE_ONE).to_string(), "-1000");
  }

  void testDivisionWithMultipleMultSubSteps() {
    math::biginteger bi{1112};
    TS_ASSERT_EQUALS((bi/2).to_string(), "556");
  }
  
  void testDivisionDroppingNumberOfCells() {
    math::biginteger bi{1000000000ULL};
    TS_ASSERT_EQUALS((bi/2).to_string(), "500000000");
  }
  
  void testDivisionByBiggerNumberIsZero() {
    math::biginteger bi{1000ULL};
    TS_ASSERT_EQUALS((bi/1001).to_string(), "0");
  }
  
  void testDivisionWithLargeNumbers() {
    math::biginteger big{"999999998000000001"};
    TS_ASSERT_EQUALS(big.to_string(), "999999998000000001");
    TS_ASSERT_EQUALS((big/999999999ULL).to_string(),
                     "999999999");
  }
  
  void testModuloZeroThrows() {
    math::biginteger bi{1000};
    TS_ASSERT_THROWS(bi%0, std::domain_error);
  }
  
  void testModuloBiggerIsSameValue() {
    math::biginteger bi{1000};
    TS_ASSERT_EQUALS(bi%2000, bi);
  }
  
  void testModuloSameNumberIsZero() {
    math::biginteger bi{1000};
    TS_ASSERT_EQUALS(bi%1000, 0);
  }

  void testModuloDivisorIsZero() {
    math::biginteger bi{1000};
    TS_ASSERT_EQUALS(bi%100, 0);
  }

  void testModuloDiffSignIsInverseElement() {
    math::biginteger bi{1000};
    math::biginteger mod{13};
    TS_ASSERT_EQUALS((bi%mod)+((-bi)%mod), mod);
  }

  void testModuloNegativesIsNegative() {
    math::biginteger bi{1000};
    math::biginteger mod{13};
    TS_ASSERT_EQUALS((bi%mod), -((-bi)%(-mod)));
  }
};