cpp-lazy-stream/test/transform_test.cxx

//
//  transform_test.cxx
//  stream-test
//
//  Created by Sam Jaffe on 4/5/23.
//

#include "stream/view/transform.h"

#include <list>

#include "stream_helpers.h"
#include "stream_matchers.h"

// Workaround for OSX and pointer-to-member-functions
template class std::basic_string<char>;

TEST(TransformView, NotRequiredToProvideSizeOrEmpty) {
  Range<std::list<int>, Sentinel> input{0, 1, 2, 3, 4};

  auto range = input | views::transform([](int i) { return i; });

  static_assert(!stream::detail::has_size_v<decltype(range)>);
  static_assert(stream::detail::has_empty_v<decltype(range)>);
}

TEST(TransformView, PropagatesSize) {
  Range<std::vector<int>, Sentinel, Sized> input{0, 1, 2, 3, 4};

  auto range = input | views::transform([](int i) { return i; });

  static_assert(stream::detail::has_size_v<decltype(range)>);
  EXPECT_THAT(range.size(), input.size());
}

TEST(TransformView, PropagatesEmpty) {
  Range<std::vector<int>, Sentinel, Sized> input{0, 1, 2, 3, 4};

  auto range = input | views::transform([](int i) { return i; });

  static_assert(stream::detail::has_empty_v<decltype(range)>);
  EXPECT_THAT(range.empty(), input.empty());
}

TEST(TransformView, ReturnsNewElements) {
  std::vector<int> const input{1, 2, 3, 4, 5};
  EXPECT_THAT(input | views::transform([](int i) { return 2 * i + 1; }),
              RangesEq(std::vector{3, 5, 7, 9, 11}));
}

TEST(TransformView, CanReturnReference) {
  std::vector<int> const input{1, 2, 3, 4, 5};

  auto range = input | views::transform([](auto & i) -> auto & { return i; });
  EXPECT_THAT(&*range.begin(), &*input.begin());
}

TEST(TransformView, CanUseMemberPtr) {
  struct test {
    int val;
  };
  std::vector<test> input{{1}, {3}, {2}};

  EXPECT_THAT(input | views::transform(&test::val),
              RangesEq(std::vector{1, 3, 2}));
}

TEST(TransformView, CanUseMemberFn) {
  std::vector<std::string> input{"hello", "goodbye"};

  EXPECT_THAT(input | views::transform(&std::string::size),
              RangesEq(std::vector{5, 7}));
}