cpp-optional-stream/test/optional_stream_test.cxx

//
//  optional_stream.t.h
//  optional.stream
//
//  Created by Sam Jaffe on 1/29/17.
//

#include <gmock/gmock.h>
#include <gtest/gtest.h>

#include "stream/optional_stream.hpp"

using ::testing::Eq;

MATCHER(Absent, "") {
  return !arg.has_value();
}

MATCHER(Present, "") {
  return arg.has_value();
}

MATCHER_P(OptionalIs, value, "") {
  return arg.has_value() && *arg == value;
}

TEST(OptionalStreamTest, processes_real) {
  auto strm = stream::optional::make_stream(5);
  auto plus2 = [](int i) { return i+2; };
  std::optional<int> out = strm.map(plus2);
  
  EXPECT_THAT(out, Present());
  EXPECT_THAT(*out, Eq(7));
}

TEST(OptionalStreamTest, NoOpWhenUsedOnNullOpts) {
  auto strm = stream::optional::make_stream<int>();
  auto fail = [](int i) { throw std::runtime_error{"nullopt"}; return i; };
  std::optional<int> out;
  
  EXPECT_NO_THROW(out = strm.map(fail));
  EXPECT_THAT(out, Absent());
}

TEST(OptionalStreamTest, FlatmapFunctionCanProduceNullOpt) {
  auto strm = stream::optional::make_stream(5);
  auto discard_odd = [](int i) {
    return i%2==0? std::optional<int>(i) : std::nullopt;
  };
  std::optional<int> out;
  
  EXPECT_NO_THROW(out = strm.flatmap(discard_odd));
  EXPECT_THAT(out, Absent());
}

TEST(OptionalStreamTest, FlatmapFunctionCanProduceRealValues) {
  auto strm = stream::optional::make_stream(6);
  auto discard_odd = [](int i) {
    return i%2==0? std::optional<int>(i) : std::nullopt;
  };
  std::optional<int> out;
  
  EXPECT_NO_THROW(out = strm.flatmap(discard_odd));
  EXPECT_THAT(out, Present());
  EXPECT_THAT(out, OptionalIs(6));
}