TestRollingNumber.cpp

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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */

/* vim: set ts=8 sts=2 et sw=2 tw=80: */

/* This Source Code Form is subject to the terms of the Mozilla Public

 * License, v. 2.0. If a copy of the MPL was not distributed with this file,

 * You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "RollingNumber.h"

#include "mozilla/Assertions.h"

#include <cstdint>

#include <gtest/gtest.h>

#include <type_traits>

using RN8 = mozilla::RollingNumber<uint8_t>;

TEST(RollingNumber, Value)

  // Value type should reflect template argument.

  static_assert(std::is_same_v<RN8::ValueType, uint8_t>);

  // Default init to 0.

  const RN8 n;

  // Access through Value().

  EXPECT_EQ(0, n.Value());

  // Conversion constructor.

  RN8 n42{42};

  EXPECT_EQ(42, n42.Value());

  // Copy Constructor.

  RN8 n42Copied{n42};

  EXPECT_EQ(42, n42Copied.Value());

  // Assignment construction.

  RN8 n42Assigned = n42;

  EXPECT_EQ(42, n42Assigned.Value());

  // Assignment.

  n42 = n;

  EXPECT_EQ(0, n42.Value());

TEST(RollingNumber, Operations)

  RN8 n;

  EXPECT_EQ(0, n.Value());

  RN8 nPreInc = ++n;

  EXPECT_EQ(1, n.Value());

  EXPECT_EQ(1, nPreInc.Value());

  RN8 nPostInc = n++;

  EXPECT_EQ(2, n.Value());

  EXPECT_EQ(1, nPostInc.Value());

  RN8 nPreDec = --n;

  EXPECT_EQ(1, n.Value());

  EXPECT_EQ(1, nPreDec.Value());

  RN8 nPostDec = n--;

  EXPECT_EQ(0, n.Value());

  EXPECT_EQ(1, nPostDec.Value());

  RN8 nPlus = n + 10;

  EXPECT_EQ(0, n.Value());

  EXPECT_EQ(10, nPlus.Value());

  n += 20;

  EXPECT_EQ(20, n.Value());

  RN8 nMinus = n - 2;

  EXPECT_EQ(20, n.Value());

  EXPECT_EQ(18, nMinus.Value());

  n -= 5;

  EXPECT_EQ(15, n.Value());

  uint8_t diff = nMinus - n;

  EXPECT_EQ(3, diff);

  // Overflows.

  n = RN8(0);

  EXPECT_EQ(0, n.Value());

  n--;

  EXPECT_EQ(255, n.Value());

  n++;

  EXPECT_EQ(0, n.Value());

  n -= 10;

  EXPECT_EQ(246, n.Value());

  n += 20;

  EXPECT_EQ(10, n.Value());

TEST(RollingNumber, Comparisons)

  uint8_t i = 0;

  do {

    RN8 n{i};

    EXPECT_EQ(i, n.Value());

    EXPECT_TRUE(n == n);

    EXPECT_FALSE(n != n);

    EXPECT_FALSE(n < n);

    EXPECT_TRUE(n <= n);

    EXPECT_FALSE(n > n);

    EXPECT_TRUE(n >= n);

    RN8 same = n;

    EXPECT_TRUE(n == same);

    EXPECT_FALSE(n != same);

    EXPECT_FALSE(n < same);

    EXPECT_TRUE(n <= same);

    EXPECT_FALSE(n > same);

    EXPECT_TRUE(n >= same);

#ifdef DEBUG

    // In debug builds, we are only allowed a quarter of the type range.

    const uint8_t maxDiff = 255 / 4;

#else

    // In non-debug builds, we can go half-way up or down the type range, and

    // still conserve the expected ordering.

    const uint8_t maxDiff = 255 / 2;

#endif

    for (uint8_t add = 1; add <= maxDiff; ++add) {

      RN8 bigger = n + add;

      EXPECT_FALSE(n == bigger);

      EXPECT_TRUE(n != bigger);

      EXPECT_TRUE(n < bigger);

      EXPECT_TRUE(n <= bigger);

      EXPECT_FALSE(n > bigger);

      EXPECT_FALSE(n >= bigger);

    for (uint8_t sub = 1; sub <= maxDiff; ++sub) {

      RN8 smaller = n - sub;

      EXPECT_FALSE(n == smaller);

      EXPECT_TRUE(n != smaller);

      EXPECT_FALSE(n < smaller);

      EXPECT_FALSE(n <= smaller);

      EXPECT_TRUE(n > smaller);

      EXPECT_TRUE(n >= smaller);

    ++i;

  } while (i != 0);