cpp-descriptive-pointers/maybe_null.t.h

//
//  maybe_null.t.h
//  pointers
//
//  Created by Sam Jaffe on 12/2/16.
//

#pragma once

#include <cxxtest/TestSuite.h>
#include <memory>

#undef DEBUG
#define DEBUG
#include "maybe_null.hpp"

class maybe_null_TestSuite : public CxxTest::TestSuite {
public:
  using ptr_base = std::shared_ptr<int>;
  using ptr_t = maybe_null<ptr_base>;
public:
  void test_can_hold_nullptr() const {
    ptr_t mn{nullptr};
    TS_ASSERT_EQUALS(bool(mn), false);
  }
  
  void test_is_valid_wo_nullptr() const {
    ptr_t mn = make_with(5);
    TS_ASSERT_EQUALS(bool(mn), true);
  }
  
  void test_nullptr_throws_or_false() const {
    ptr_t mn{nullptr};
    TS_ASSERT_THROWS(*mn, unchecked_pointer_exception);
  }
  
  void test_object_contains_ptr() const {
    ptr_base i{new int};
    ptr_t n{i};
    TS_ASSERT_EQUALS(bool(n), true);
    TS_ASSERT_EQUALS(n.get(), i.get());
    TS_ASSERT_EQUALS(*n, *i);
  }
  
  void test_object_sets_value() const {
    static int const value1{5};
    static int const value2{4};
    
    ptr_base i{new int{value1}};
    ptr_t n{i};
    TS_ASSERT_EQUALS(bool(n), true);
    TS_ASSERT_EQUALS(*n, value1);
    *n = value2;
    TS_ASSERT_EQUALS(bool(n), true);
    TS_ASSERT_EQUALS(*i, value2);
  }
  
  void test_do_not_own() const {
    bool has_delete{false};
    struct test_t {
      ~test_t() { _r = true; }
      bool & _r;
    };
    {
      std::shared_ptr<test_t> test_struct{new test_t{has_delete}};
    
      TS_ASSERT_EQUALS(test_struct->_r, has_delete);
      {
      maybe_null<std::shared_ptr<test_t>> nn(test_struct);
      }
      TS_ASSERT_EQUALS(has_delete, false);
    }
    TS_ASSERT_EQUALS(has_delete, true);
  }
  
  void test_type_conversion() {
    struct base {};
    struct derived : public base {};
    derived d;
    maybe_null<derived*> m{&d};
    maybe_null<base*> b = maybe_null<base*>(m);
    TS_ASSERT_EQUALS(b.get(), m.get());
  }
  
private:
  template <typename T>
  static maybe_null<std::shared_ptr<T>> make_with(T p) {
    return maybe_null<std::shared_ptr<T>>(std::make_shared<T>(p));
  }
};