From de5d0cbb9c58852ff0038be5495fa7e5d656dd1d Mon Sep 17 00:00:00 2001
From: Felix Morgner <felix.morgner@gmail.com>
Date: Thu, 2 Jan 2020 11:43:54 +0100
Subject: new_type: implement subtraction

---
 test/src/arithmetic_suite.cpp | 37 +++++++++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)

(limited to 'test')

diff --git a/test/src/arithmetic_suite.cpp b/test/src/arithmetic_suite.cpp
index 4541125..57c06e8 100644
--- a/test/src/arithmetic_suite.cpp
+++ b/test/src/arithmetic_suite.cpp
@@ -40,6 +40,37 @@ inline namespace addition_tests
 
 }  // namespace addition_tests
 
+inline namespace subtraction_tests
+{
+
+  auto a_new__type_not_deriving_arithmetic_is_not_subtractable_with_instances_of_itself() -> void
+  {
+    using type_alias = nt::new_type<int, struct tag>;
+    ASSERT(!(nt::impl::is_subtractable_v<type_alias>));
+  }
+
+  auto a_new__type_deriving_arithmetic_is_subtractable_with_instances_of_itself() -> void
+  {
+    using type_alias = nt::new_type<int, struct tag, deriving(nt::Arithmetic)>;
+    ASSERT(nt::impl::is_subtractable_v<type_alias>);
+  }
+
+  auto subtraction_of_two_instances_of_a_new__type_deriving_arithmetic_produces_an_instance_of_the_same_new__type() -> void
+  {
+    using type_alias = nt::new_type<int, struct tag, deriving(nt::Arithmetic)>;
+    ASSERT((std::is_same_v<type_alias, decltype(std::declval<type_alias const &>() + std::declval<type_alias const &>())>));
+  }
+
+  auto subtraction_of_two_instances_of_a_new__type_deriving_arithmetic_produces_the_correct_value_with_respect_to_the_base_type() -> void
+  {
+    using type_alias = nt::new_type<int, struct tag, deriving(nt::Arithmetic)>;
+    auto lhs = type_alias{24};
+    auto rhs = type_alias{18};
+    ASSERT_EQUAL(24 - 18, (lhs - rhs).decay());
+  }
+
+}  // namespace subtraction_tests
+
 auto arithmetic_suite() -> std::pair<cute::suite, std::string>
 {
   return {{
@@ -48,6 +79,12 @@ auto arithmetic_suite() -> std::pair<cute::suite, std::string>
               KAWAII(a_new__type_deriving_arithmetic_is_addable_with_instances_of_itself),
               KAWAII(addition_of_two_instances_of_a_new__type_deriving_arithmetic_produces_an_instance_of_the_same_new__type),
               KAWAII(addition_of_two_instances_of_a_new__type_deriving_arithmetic_produces_the_correct_value_with_respect_to_the_base_type),
+
+              /// Subtraction Tests
+              KAWAII(a_new__type_not_deriving_arithmetic_is_not_subtractable_with_instances_of_itself),
+              KAWAII(a_new__type_deriving_arithmetic_is_subtractable_with_instances_of_itself),
+              KAWAII(subtraction_of_two_instances_of_a_new__type_deriving_arithmetic_produces_an_instance_of_the_same_new__type),
+              KAWAII(subtraction_of_two_instances_of_a_new__type_deriving_arithmetic_produces_the_correct_value_with_respect_to_the_base_type),
           },
           "Arithmetic Operators Tests"};
 }
\ No newline at end of file
-- 
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