Add Wrapper (#179)

* Update copyright year

* Alias: added

* bump release-drafter from 5.11.0 to 5.14.0

* Version set to 2.3.0

* Rename Alias as Wrapper and drop map method

Simplify tests.

.github/workflows/draft-release.yml

@@ -9,6 +9,6 @@ jobs:
   update_draft_release:
     runs-on: ubuntu-latest
     steps:
-      - uses: release-drafter/release-drafter@v5.11.0
+      - uses: release-drafter/release-drafter@v5.14.0
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}

LICENSE.txt

@@ -1,7 +1,7 @@
 /**
  * The MIT License (MIT)
  *
- * Copyright (c) 2018 Paul Campbell
+ * Copyright (c) 2021 Paul Campbell
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy of this software
  * and associated documentation files (the "Software"), to deal in the Software without restriction,

README.org

@@ -1,11 +1,12 @@
 * Mon
-* TypeAlias, Maybe and Result for Java.
+* Alias, TypeAlias, Maybe and Result for Java.
 
   [[https://oss.sonatype.org/content/repositories/releases/net/kemitix/mon][file:https://img.shields.io/nexus/r/https/oss.sonatype.org/net.kemitix/mon.svg?style=for-the-badge]]
   [[https://search.maven.org/#search%7Cga%7C1%7Cg%3A%22net.kemitix%22%20AND%20a%3A%22mon%22][file:https://img.shields.io/maven-central/v/net.kemitix/mon.svg?style=for-the-badge]]
   [[http://i.jpeek.org/net.kemitix/mon/index.html][file:http://i.jpeek.org/net.kemitix/mon/badge.svg]]
 
   - [Maven Usage]
+  - [Alias]
   - [TypeAlias]
   - [Maybe]
   - [Result]
@@ -26,7 +27,10 @@
     The latest version should be shown above with the nexus and maven-central
     badges or can be found on [[https://search.maven.org/#search%7Cga%7C1%7Cg%3A%22net.kemitix%22%20AND%20a%3A%22mon%22][Maven Central]].
 
-* TypeAlias
+* Wrapper
+
+  A simple FunctionalInterface that contains a value. Can be used to implement
+  a form of type-alias in Java.
 
   In Haskell it is possible to create an alias for a Type, and to then use
   that alias with the same behaviour as the original, except that the compiler
@@ -40,19 +44,61 @@
     newtype PhoneBook = PhoneBook [PhoneBookEntry]
   #+END_SRC
 
-  In Java we don't have the ability to have that true alias, so TypeAlias is
-  more of a type-wrapper. It's as close as I could get to a Haskell type alias
-  in Java.
+  In Java we don't have the ability to have that true alias, so Wrapper simply
+  wraps the value within a new type. It's as close as I could get to a Haskell
+  type alias in Java.
 
-  The benefits of using TypeAlias are:
+  The benefits of using Wrapper are:
 
   - encapsulation of the wrapped type when passing references through code
     that doesn't need to access the actual value, but only to pass it on
   - type-safe parameters where you would otherwise be passing Strings,
     Integers, Lists, or other general classes
-  - equality and hashcode
   - less verbose than implementing your own
 
+  *Wrapper Example:*
+
+  #+BEGIN_SRC java
+  interface PhoneNumber extends Wrapper<String> {}
+
+  PhoneNumber pn = () -> "01234 567890";
+  String v = pn.value();
+  #+END_SRC
+
+  *Roll your own:*
+
+  #+BEGIN_SRC java
+  class PhoneNumber {
+      private final String value;
+      public PhoneNumber(final String value) {
+          this.value = value;
+      }
+      public String value() {
+          return value;
+      }
+  }
+  #+END_SRC
+
+  *Lombok:*
+
+  Using Lombok we can achieve it in 8 lines, compared to 24 for rolling your
+  own, or 1 for Alias:
+
+  #+BEGIN_SRC java
+  @Value
+  @RequiredArgsConstructor(access = AccessLevel.PRIVATE)
+  class PhoneNumber {
+      private final String value;
+      public static PhoneNumber of(final String phoneNumber) {
+          return new PhoneNumber(phoneNumber);
+      }
+  }
+  #+END_SRC
+
+* TypeAlias
+
+  Note: this is a precursor to `Wrapper` and should be considered deprecated.
+
   *TypeAlias Example:*
 
   #+BEGIN_SRC java
@@ -66,51 +112,6 @@
   }
   #+END_SRC
 
-  *Roll your own:*
-
-  #+BEGIN_SRC java
-  class PhoneNumber {
-      private final String value;
-      private PhoneNumber(final String value) {
-          this.value = value;
-      }
-      public static PhoneNumber of(final String phoneNumber) {
-          return new PhoneNumber(phoneNumber);
-      }
-      @Override
-      public boolean equals(Object o) {
-          if (this == o) return true;
-          if (o == null || getClass() != o.getClass()) return false;
-          PhoneNumber that = (PhoneNumber) o;
-          return Objects.equals(value, that.value);
-      }
-      @Override
-      public int hashCode() {
-          return Objects.hash(value);
-      }
-      public String getValue() {
-          return value;
-      }
-  }
-  #+END_SRC
-
-  *Lombok:*
-
-  Although, if you are using Lombok, that can be equally terse, both it and
-  TypeAlias<String> coming in at 8 lines each, compared to 24 for rolling your
-  own:
-
-  #+BEGIN_SRC java
-  @Value
-  @RequiredArgsConstructor(access = AccessLevel.PRIVATE)
-  class PhoneNumber {
-      private final String value;
-      public static PhoneNumber of(final String phoneNumber) {
-          return new PhoneNumber(phoneNumber);
-      }
-  }
-  #+END_SRC
-
 ** =TypeAlias= *can* be a Monad
 
    #+BEGIN_SRC java

pom.xml

@@ -11,7 +11,7 @@
     </parent>
 
     <artifactId>mon</artifactId>
-    <version>2.2.1-SNAPSHOT</version>
+    <version>2.3.0</version>
 
     <name>Mon</name>
     <description>TypeAlias, Result and Maybe for Java</description>

src/main/java/net/kemitix/mon/Functor.java

@@ -1,7 +1,7 @@
 /**
  * The MIT License (MIT)
  *
- * Copyright (c) 2018 Paul Campbell
+ * Copyright (c) 2021 Paul Campbell
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy of this software
  * and associated documentation files (the "Software"), to deal in the Software without restriction,

src/main/java/net/kemitix/mon/Mon.java

@@ -1,7 +1,7 @@
 /**
  * The MIT License (MIT)
  *
- * Copyright (c) 2018 Paul Campbell
+ * Copyright (c) 2021 Paul Campbell
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy of this software
  * and associated documentation files (the "Software"), to deal in the Software without restriction,

src/main/java/net/kemitix/mon/TypeAlias.java

@@ -1,7 +1,7 @@
 /**
  * The MIT License (MIT)
  *
- * Copyright (c) 2018 Paul Campbell
+ * Copyright (c) 2021 Paul Campbell
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy of this software
  * and associated documentation files (the "Software"), to deal in the Software without restriction,

src/main/java/net/kemitix/mon/Wrapper.java

@@ -0,0 +1,42 @@
+/**
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2021 Paul Campbell
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of this software
+ * and associated documentation files (the "Software"), to deal in the Software without restriction,
+ * including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all copies
+ * or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
+ * INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE
+ * AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+ * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+package net.kemitix.mon;
+
+/**
+ * A wrapper for other types.
+ *
+ * <p>Can be used as a form of type-alias, where the value is held in the wrapper.</p>
+ *
+ * @param <T> the type of the wrapper's value
+ * @author Paul Campbell (pcampbell@kemitix.net)
+ */
+@FunctionalInterface
+public interface Wrapper<T> {
+
+    /**
+     * The wrapped value.
+     *
+     * @return the value
+     */
+    public abstract T value();
+
+}

src/main/java/net/kemitix/mon/combinator/After.java

@@ -1,7 +1,7 @@
 /**
  * The MIT License (MIT)
  *
- * Copyright (c) 2018 Paul Campbell
+ * Copyright (c) 2021 Paul Campbell
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy of this software
  * and associated documentation files (the "Software"), to deal in the Software without restriction,

src/main/java/net/kemitix/mon/combinator/Around.java

@@ -1,7 +1,7 @@
 /**
  * The MIT License (MIT)
  *
- * Copyright (c) 2018 Paul Campbell
+ * Copyright (c) 2021 Paul Campbell
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy of this software
  * and associated documentation files (the "Software"), to deal in the Software without restriction,

src/main/java/net/kemitix/mon/combinator/Before.java

@@ -1,7 +1,7 @@
 /**
  * The MIT License (MIT)
  *
- * Copyright (c) 2018 Paul Campbell
+ * Copyright (c) 2021 Paul Campbell
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy of this software
  * and associated documentation files (the "Software"), to deal in the Software without restriction,

src/main/java/net/kemitix/mon/combinator/package-info.java

@@ -1,7 +1,7 @@
 /**
  * The MIT License (MIT)
  *
- * Copyright (c) 2018 Paul Campbell
+ * Copyright (c) 2021 Paul Campbell
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy of this software
  * and associated documentation files (the "Software"), to deal in the Software without restriction,

src/main/java/net/kemitix/mon/experimental/BeanBuilder.java

@@ -1,7 +1,7 @@
 /**
  * The MIT License (MIT)
  *
- * Copyright (c) 2018 Paul Campbell
+ * Copyright (c) 2021 Paul Campbell
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy of this software
  * and associated documentation files (the "Software"), to deal in the Software without restriction,

src/main/java/net/kemitix/mon/experimental/either/Either.java

@@ -1,7 +1,7 @@
 /**
  * The MIT License (MIT)
  *
- * Copyright (c) 2018 Paul Campbell
+ * Copyright (c) 2021 Paul Campbell
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy of this software
  * and associated documentation files (the "Software"), to deal in the Software without restriction,

src/main/java/net/kemitix/mon/experimental/either/Left.java

@@ -1,7 +1,7 @@
 /**
  * The MIT License (MIT)
  *
- * Copyright (c) 2018 Paul Campbell
+ * Copyright (c) 2021 Paul Campbell
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy of this software
  * and associated documentation files (the "Software"), to deal in the Software without restriction,

src/main/java/net/kemitix/mon/experimental/either/Right.java

@@ -1,7 +1,7 @@
 /**
  * The MIT License (MIT)
  *
- * Copyright (c) 2018 Paul Campbell
+ * Copyright (c) 2021 Paul Campbell
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy of this software
  * and associated documentation files (the "Software"), to deal in the Software without restriction,

src/main/java/net/kemitix/mon/experimental/either/package-info.java

@@ -1,7 +1,7 @@
 /**
  * The MIT License (MIT)
  *
- * Copyright (c) 2018 Paul Campbell
+ * Copyright (c) 2021 Paul Campbell
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy of this software
  * and associated documentation files (the "Software"), to deal in the Software without restriction,

src/main/java/net/kemitix/mon/experimental/package-info.java

@@ -1,7 +1,7 @@
 /**
  * The MIT License (MIT)
  *
- * Copyright (c) 2018 Paul Campbell
+ * Copyright (c) 2021 Paul Campbell
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy of this software
  * and associated documentation files (the "Software"), to deal in the Software without restriction,

src/main/java/net/kemitix/mon/lazy/Lazy.java

@@ -1,7 +1,7 @@
 /**
  * The MIT License (MIT)
  *
- * Copyright (c) 2018 Paul Campbell
+ * Copyright (c) 2021 Paul Campbell
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy of this software
  * and associated documentation files (the "Software"), to deal in the Software without restriction,

src/main/java/net/kemitix/mon/lazy/LazySupplier.java

@@ -1,7 +1,7 @@
 /**
  * The MIT License (MIT)
  *
- * Copyright (c) 2018 Paul Campbell
+ * Copyright (c) 2021 Paul Campbell
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy of this software
  * and associated documentation files (the "Software"), to deal in the Software without restriction,

src/main/java/net/kemitix/mon/lazy/package-info.java

@@ -1,7 +1,7 @@
 /**
  * The MIT License (MIT)
  *
- * Copyright (c) 2018 Paul Campbell
+ * Copyright (c) 2021 Paul Campbell
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy of this software
  * and associated documentation files (the "Software"), to deal in the Software without restriction,

src/main/java/net/kemitix/mon/maybe/Just.java

@@ -1,7 +1,7 @@
 /**
  * The MIT License (MIT)
  *
- * Copyright (c) 2018 Paul Campbell
+ * Copyright (c) 2021 Paul Campbell
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy of this software
  * and associated documentation files (the "Software"), to deal in the Software without restriction,

src/main/java/net/kemitix/mon/maybe/Maybe.java

@@ -1,7 +1,7 @@
 /**
  * The MIT License (MIT)
  *
- * Copyright (c) 2018 Paul Campbell
+ * Copyright (c) 2021 Paul Campbell
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy of this software
  * and associated documentation files (the "Software"), to deal in the Software without restriction,

src/main/java/net/kemitix/mon/maybe/Nothing.java

@@ -1,7 +1,7 @@
 /**
  * The MIT License (MIT)
  *
- * Copyright (c) 2018 Paul Campbell
+ * Copyright (c) 2021 Paul Campbell
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy of this software
  * and associated documentation files (the "Software"), to deal in the Software without restriction,

src/main/java/net/kemitix/mon/maybe/package-info.java

@@ -1,7 +1,7 @@
 /**
  * The MIT License (MIT)
  *
- * Copyright (c) 2018 Paul Campbell
+ * Copyright (c) 2021 Paul Campbell
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy of this software
  * and associated documentation files (the "Software"), to deal in the Software without restriction,

src/main/java/net/kemitix/mon/package-info.java

@@ -1,7 +1,7 @@
 /**
  * The MIT License (MIT)
  *
- * Copyright (c) 2018 Paul Campbell
+ * Copyright (c) 2021 Paul Campbell
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy of this software
  * and associated documentation files (the "Software"), to deal in the Software without restriction,

src/main/java/net/kemitix/mon/result/CheckedErrorResultException.java

@@ -1,7 +1,7 @@
 /**
  * The MIT License (MIT)
  *
- * Copyright (c) 2018 Paul Campbell
+ * Copyright (c) 2021 Paul Campbell
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy of this software
  * and associated documentation files (the "Software"), to deal in the Software without restriction,

src/main/java/net/kemitix/mon/result/Err.java

@@ -1,7 +1,7 @@
 /**
  * The MIT License (MIT)
  *
- * Copyright (c) 2018 Paul Campbell
+ * Copyright (c) 2021 Paul Campbell
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy of this software
  * and associated documentation files (the "Software"), to deal in the Software without restriction,

src/main/java/net/kemitix/mon/result/ErrorResultException.java

@@ -1,7 +1,7 @@
 /**
  * The MIT License (MIT)
  *
- * Copyright (c) 2018 Paul Campbell
+ * Copyright (c) 2021 Paul Campbell
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy of this software
  * and associated documentation files (the "Software"), to deal in the Software without restriction,

src/main/java/net/kemitix/mon/result/Result.java

@@ -1,7 +1,7 @@
 /**
  * The MIT License (MIT)
  *
- * Copyright (c) 2018 Paul Campbell
+ * Copyright (c) 2021 Paul Campbell
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy of this software
  * and associated documentation files (the "Software"), to deal in the Software without restriction,

src/main/java/net/kemitix/mon/result/Success.java

@@ -1,7 +1,7 @@
 /**
  * The MIT License (MIT)
  *
- * Copyright (c) 2018 Paul Campbell
+ * Copyright (c) 2021 Paul Campbell
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy of this software
  * and associated documentation files (the "Software"), to deal in the Software without restriction,

src/main/java/net/kemitix/mon/result/UnexpectedErrorResultException.java

@@ -1,7 +1,7 @@
 /**
  * The MIT License (MIT)
  *
- * Copyright (c) 2018 Paul Campbell
+ * Copyright (c) 2021 Paul Campbell
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy of this software
  * and associated documentation files (the "Software"), to deal in the Software without restriction,

src/main/java/net/kemitix/mon/result/WithResultContinuation.java

@@ -1,7 +1,7 @@
 /**
  * The MIT License (MIT)
  *
- * Copyright (c) 2018 Paul Campbell
+ * Copyright (c) 2021 Paul Campbell
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy of this software
  * and associated documentation files (the "Software"), to deal in the Software without restriction,

src/main/java/net/kemitix/mon/result/package-info.java

@@ -1,7 +1,7 @@
 /**
  * The MIT License (MIT)
  *
- * Copyright (c) 2018 Paul Campbell
+ * Copyright (c) 2021 Paul Campbell
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy of this software
  * and associated documentation files (the "Software"), to deal in the Software without restriction,

src/main/java/net/kemitix/mon/tree/GeneralisedTree.java

@@ -1,7 +1,7 @@
 /**
  * The MIT License (MIT)
  *
- * Copyright (c) 2018 Paul Campbell
+ * Copyright (c) 2021 Paul Campbell
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy of this software
  * and associated documentation files (the "Software"), to deal in the Software without restriction,

src/main/java/net/kemitix/mon/tree/MutableTree.java

@@ -1,7 +1,7 @@
 /**
  * The MIT License (MIT)
  *
- * Copyright (c) 2018 Paul Campbell
+ * Copyright (c) 2021 Paul Campbell
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy of this software
  * and associated documentation files (the "Software"), to deal in the Software without restriction,

src/main/java/net/kemitix/mon/tree/MutableTreeBuilder.java

@@ -1,7 +1,7 @@
 /**
  * The MIT License (MIT)
  *
- * Copyright (c) 2018 Paul Campbell
+ * Copyright (c) 2021 Paul Campbell
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy of this software
  * and associated documentation files (the "Software"), to deal in the Software without restriction,

src/main/java/net/kemitix/mon/tree/Tree.java

@@ -1,7 +1,7 @@
 /**
  * The MIT License (MIT)
  *
- * Copyright (c) 2018 Paul Campbell
+ * Copyright (c) 2021 Paul Campbell
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy of this software
  * and associated documentation files (the "Software"), to deal in the Software without restriction,

src/main/java/net/kemitix/mon/tree/TreeBuilder.java

@@ -1,7 +1,7 @@
 /**
  * The MIT License (MIT)
  *
- * Copyright (c) 2018 Paul Campbell
+ * Copyright (c) 2021 Paul Campbell
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy of this software
  * and associated documentation files (the "Software"), to deal in the Software without restriction,

src/main/java/net/kemitix/mon/tree/TreeMapper.java

@@ -1,7 +1,7 @@
 /**
  * The MIT License (MIT)
  *
- * Copyright (c) 2018 Paul Campbell
+ * Copyright (c) 2021 Paul Campbell
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy of this software
  * and associated documentation files (the "Software"), to deal in the Software without restriction,

src/main/java/net/kemitix/mon/tree/package-info.java

@@ -1,7 +1,7 @@
 /**
  * The MIT License (MIT)
  *
- * Copyright (c) 2018 Paul Campbell
+ * Copyright (c) 2021 Paul Campbell
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy of this software
  * and associated documentation files (the "Software"), to deal in the Software without restriction,

src/test/java/net/kemitix/mon/Address.java

@@ -1,7 +1,7 @@
 /**
  * The MIT License (MIT)
  *
- * Copyright (c) 2018 Paul Campbell
+ * Copyright (c) 2021 Paul Campbell
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy of this software
  * and associated documentation files (the "Software"), to deal in the Software without restriction,

src/test/java/net/kemitix/mon/Customer.java

@@ -1,7 +1,7 @@
 /**
  * The MIT License (MIT)
  *
- * Copyright (c) 2018 Paul Campbell
+ * Copyright (c) 2021 Paul Campbell
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy of this software
  * and associated documentation files (the "Software"), to deal in the Software without restriction,

src/test/java/net/kemitix/mon/WrapperTest.java

@@ -0,0 +1,83 @@
+package net.kemitix.mon;
+
+import org.junit.jupiter.api.Disabled;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class WrapperTest {
+
+    interface WrappedString extends Wrapper<String> {}
+
+    interface WrappedInteger extends Wrapper<Integer> {}
+
+    interface WrappedIterableString extends Wrapper<Iterable<String>> { }
+
+    interface WrappedListInteger extends Wrapper<List<Integer>> {}
+
+    interface AWrapper extends Wrapper<String> {}
+
+    @Test
+    void shouldCreateAWrapperAndGetTheValue() {
+        //given
+        final String value = "value";
+        //when
+        // - anonymous class syntax
+        final WrappedString wrappedString = new WrappedString() {
+            @Override
+            public String value() {
+                return value;
+            }
+        };
+        //then
+        assertThat(wrappedString.value()).isSameAs(value);
+    }
+
+    @Test
+    void shouldCreateAWrapperWithNestedGenericTypes() {
+        //given
+        final Iterable<String> iterable = Collections.emptyList();
+        //when
+        // - functional interface / lambda syntax
+        final WrappedIterableString wrappedIterableString = () -> iterable;
+        //then
+        assertThat(wrappedIterableString.value()).isSameAs(iterable);
+    }
+
+    @Test
+    void shouldCreateAWrapperSubclassAndGetTheValue() {
+        //given
+        final String value = "value";
+        //when
+        final AWrapper aWrapper = () -> value;
+        //then
+        assertThat(aWrapper.value()).isSameAs(value);
+    }
+
+    @Test
+    void shouldNotBeEqualWhenValueTypesAreDifferent() {
+        //given
+        final WrappedString wrappedString = () -> "1";
+        final WrappedInteger wrappedInteger = () -> 1;
+        //then
+        assertThat(wrappedString).isNotEqualTo(wrappedInteger);
+    }
+
+    @Test
+    void shouldNotBeEqualEvenWhenValuesAreTheSame() {
+        //given
+        final String value = "value";
+        final AWrapper aWrapper1 = () -> value;
+        final AWrapper aWrapper2 = () -> value;
+        //then
+        assertThat(aWrapper1).isNotEqualTo(aWrapper2);
+        // instead compare `.value()`s
+        assertThat(aWrapper1.value()).isEqualTo(aWrapper2.value());
+    }
+
+}