cpp-lazy-stream/test/filter_test.cxx

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

#include "stream/view/filter.h"

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

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

  auto range = input | views::filter([](int) { return true; });
  static_assert(!stream::detail::has_size_v<decltype(range)>);
}

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

  auto range = input | views::filter([](int) { return true; });
  static_assert(stream::detail::has_empty_v<decltype(range)>);
}

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

  EXPECT_THAT(input | views::filter([](int) { return true; }), RangesEq(input));
}

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

  EXPECT_THAT(input | views::filter([](int i) { return i % 2 == 0; }),
              RangesEq(std::vector{2, 4}));
}