Add Reader.flatMap() (#228)

* Add link to online Javadoc.

* Add Reader.flatMap

.github/workflows/build-maven.yml

@@ -15,7 +15,7 @@ jobs:
     steps:
       - uses: actions/checkout@v2
       - name: setup-jdk-${{ matrix.java }}
-        uses: actions/setup-java@v2.1.0
+        uses: actions/setup-java@v2.2.0
         with:
           distribution: 'adopt'
           java-version: ${{ matrix.java }}

.github/workflows/deploy-sonatype.yml

@@ -12,7 +12,7 @@ jobs:
     steps:
       - uses: actions/checkout@v2
       - name: Set up JDK
-        uses: actions/setup-java@v2.1.0
+        uses: actions/setup-java@v2.2.0
         with:
           distribution: 'adopt'
           java-version: 11

README.md

@@ -14,6 +14,8 @@ https://oss.sonatype.org/content/repositories/releases/net/kemitix/mon/)
 https://img.shields.io/maven-central/v/net.kemitix/mon.svg?style=for-the-badge)](
 https://search.maven.org/artifact/net.kemitix/mon)
 
+The documentation below is being slowly migrated to [Javadoc](https://kemitix.github.io/mon/).
+
 - [Maven Usage](#Maven-Usage)
 - [Wrapper](#Wrapper) - light-weight type-alias-like
 - [TypeAlias](#TypeAlias) - type-alias-like monadic wrapper

pom.xml

@@ -11,7 +11,7 @@
     </parent>
 
     <artifactId>mon</artifactId>
-    <version>3.0.0</version>
+    <version>3.3.0</version>
 
     <name>Mon</name>
     <description>Wrapper, TypeAlias, Maybe, Result, Tree, Lazy, Either and Combinators for Java.
@@ -41,9 +41,9 @@
         <kemitix-maven-tiles.version>3.0.1</kemitix-maven-tiles.version>
         <digraph-dependency.basePackage>net.kemitix.mon</digraph-dependency.basePackage>
         <kemitix-checkstyle.version>5.5.0</kemitix-checkstyle.version>
-        <pitest-maven-plugin.version>1.6.8</pitest-maven-plugin.version>
+        <pitest-maven-plugin.version>1.6.9</pitest-maven-plugin.version>
         <pitest-junit5-plugin.version>0.14</pitest-junit5-plugin.version>
-        <spotbugs.version>4.3.0</spotbugs.version>
+        <spotbugs.version>4.4.0</spotbugs.version>
         <apiguardian-api.version>1.1.2</apiguardian-api.version>
     </properties>
 
@@ -60,7 +60,6 @@
             <artifactId>apiguardian-api</artifactId>
             <version>${apiguardian-api.version}</version>
         </dependency>
-
         <dependency>
             <groupId>org.junit.jupiter</groupId>
             <artifactId>junit-jupiter-api</artifactId>

src/main/java/net/kemitix/mon/reader/Reader.java

@@ -0,0 +1,64 @@
+package net.kemitix.mon.reader;
+
+import org.apiguardian.api.API;
+
+import java.util.function.BiFunction;
+import java.util.function.Function;
+
+/**
+ * Returns a program ready to run upon the supply of a suitable environment.
+ *
+ * @param <E> The type of the environment required by the program.
+ * @param <R> The type of the result returned by the program.
+ */
+@API(status = API.Status.EXPERIMENTAL, since = "3.0.1")
+@FunctionalInterface
+public interface Reader<E, R> {
+
+    /**
+     * Executes the program.
+     *
+     * @param env the required environment
+     * @return the result of the program
+     */
+    R run(E env);
+
+    /**
+     * Applies the function provided to the reader when it is run.
+     *
+     * @param f the function, which takes an {@link E} as its only parameter
+     * @param <V> the type of the functions output
+     * @return a new Reader to provide the result of the supplied function
+     */
+    @API(status = API.Status.EXPERIMENTAL)
+    default <V> Reader<E, V> map(Function<R, V> f) {
+        return e -> f.apply(run(e));
+    }
+
+    /**
+     * Applies the function provided to the reader when it is run.
+     *
+     * @param f the function, which takes an {@link E} and the previously
+     *          generated value as its two parameters
+     * @param <V> the type of the functions output
+     * @return a new Reader to provided the result of the supplied function
+     */
+    @API(status = API.Status.EXPERIMENTAL)
+    default <V> Reader<E, V> flatMap(BiFunction<E, R, V> f) {
+        return env -> f.apply(env, run(env));
+    }
+
+    /**
+     * Applies the function provided to the reader when run, and executes that
+     * resulting reader.
+     *
+     * @param f the function which takes the previously generated value and
+     *          produces another Reader
+     * @param <V> the type of the value the new Reader returns
+     * @return a new Reader
+     */
+    @API(status = API.Status.EXPERIMENTAL)
+    default <V> Reader<E, V> flatMap(Function<R, Reader<E, V>> f) {
+        return env -> f.apply(run(env)).run(env);
+    }
+}

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

@@ -0,0 +1 @@
+package net.kemitix.mon.reader;

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

@@ -24,7 +24,6 @@ package net.kemitix.mon.result;
 import lombok.RequiredArgsConstructor;
 
 import java.util.Objects;
-import java.util.concurrent.Callable;
 import java.util.function.BinaryOperator;
 import java.util.function.Consumer;
 import java.util.function.Function;
@@ -67,8 +66,9 @@ class Err<T> implements Result<T> {
     }
 
     @Override
-    public void match(final Consumer<T> onSuccess, final Consumer<Throwable> onError) {
+    public Result<T> match(final Consumer<T> onSuccess, final Consumer<Throwable> onError) {
         onError.accept(error);
+        return this;
     }
 
     @Override
@@ -101,8 +101,8 @@ class Err<T> implements Result<T> {
     }
 
     @Override
-    public void onSuccess(final Consumer<T> successConsumer) {
+    public Result<T> onSuccess(final Consumer<T> successConsumer) {
-        // do nothing
+        return this;
     }
 
     @Override
@@ -122,11 +122,6 @@ class Err<T> implements Result<T> {
         return this;
     }
 
-    @Override
-    public <R> Result<R> andThen(final Function<T, Callable<R>> f) {
-        return (Result<R>) this;
-    }
-
     @Override
     public Result<T> thenWith(final Function<T, WithResultContinuation<T>> f) {
         return this;

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

@@ -26,11 +26,12 @@ public class ErrVoid implements ResultVoid {
     }
 
     @Override
-    public void match(
+    public ResultVoid match(
             final Runnable onSuccess,
             final Consumer<Throwable> onError
     ) {
         onError.accept(error);
+        return this;
     }
 
     @Override
@@ -39,8 +40,8 @@ public class ErrVoid implements ResultVoid {
     }
 
     @Override
-    public void onSuccess(final Runnable runnable) {
+    public ResultVoid onSuccess(final Runnable runnable) {
-        // do nothing
+        return this;
     }
 
     @Override

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

@@ -446,23 +446,6 @@ public interface Result<T> extends BaseResult, ThrowableFunctor<T, ThrowableFunc
         return maybeResult.flatMap(f);
     }
 
-    /**
-     * Swaps the inner {@code Result} of a {@link Maybe}, so that a {@code Result} contains a {@code Maybe}.
-     *
-     * @param maybeResult the Maybe the contains a Result
-     * @param <T>         the type of the value that may be in the Result
-     * @return a Result containing a Maybe, the value in the Maybe was the value in a successful Result within the
-     * original Maybe. If the original Maybe is Nothing, the Result will contain Nothing. If the original Result was an
-     * error, then the Result will also be an error.
-     * @deprecated
-     */
-    @API(status = DEPRECATED)
-    @Deprecated
-    static <T> Result<Maybe<T>> swap(final Maybe<Result<T>> maybeResult) {
-        return maybeResult.orElseGet(() -> Result.ok(null))
-                .flatMap(value -> Result.ok(Maybe.maybe(value)));
-    }
-
     /**
      * Creates a {@link Maybe} from the {@code Result}.
      *
@@ -657,9 +640,10 @@ public interface Result<T> extends BaseResult, ThrowableFunctor<T, ThrowableFunc
      *
      * @param onSuccess the Consumer to pass the value of a successful Result to
      * @param onError   the Consumer to pass the error from an error Result to
+     * @return the original Result
      */
     @API(status = STABLE)
-    void match(Consumer<T> onSuccess, Consumer<Throwable> onError);
+    Result<T> match(Consumer<T> onSuccess, Consumer<Throwable> onError);
 
     /**
      * Provide the value within the Result, if it is a success, to the Consumer, and returns this Result.
@@ -707,9 +691,10 @@ public interface Result<T> extends BaseResult, ThrowableFunctor<T, ThrowableFunc
      * success value. When this is an error, then nothing happens.</p>
      *
      * @param successConsumer the consumer to handle the success
+     * @return the original Result
      */
     @API(status = STABLE)
-    void onSuccess(Consumer<T> successConsumer);
+    Result<T> onSuccess(Consumer<T> successConsumer);
 
     /**
      * A handler for error state, when the error matches the errorClass.
@@ -738,29 +723,6 @@ public interface Result<T> extends BaseResult, ThrowableFunctor<T, ThrowableFunc
             Consumer<E> consumer
     );
 
-    /**
-     * Maps a Success Result to another Result using a Callable that is able to throw a checked exception.
-     *
-     * <p>Combination of {@link #flatMap(Function)} and {@link #of(Callable)}.</p>
-     *
-     * <pre><code>
-     * Integer doSomething() {...}
-     * String doSomethingElse(final Integer value) {...}
-     * Result&lt;String&gt; r = Result.of(() -&gt; doSomething())
-     *                          .andThen(value -&gt; () -&gt; doSomethingElse(value));
-     * </code></pre>
-     *
-     * <p>When the Result is an Err, then the original error is carried over and the Callable is never called.</p>
-     *
-     * @param f   the function to map the Success value into the Callable
-     * @param <R> the type of the final Result
-     * @return a new Result
-     * @deprecated Use {@link #map(ThrowableFunction)}
-     */
-    @API(status = DEPRECATED)
-    @Deprecated
-    <R> Result<R> andThen(Function<T, Callable<R>> f);
-
     /**
      * Perform the continuation with the value within the success {@code Result}
      * and return itself.

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

@@ -27,9 +27,10 @@ public interface ResultVoid extends BaseResult {
      *
      * @param onSuccess the Consumer to pass the value of a successful Result to
      * @param onError   the Consumer to pass the error from an error Result to
+     * @return the original ResultVoid
      */
     @API(status = STABLE)
-    void match(Runnable onSuccess, Consumer<Throwable> onError);
+    ResultVoid match(Runnable onSuccess, Consumer<Throwable> onError);
 
     /**
      * Attempts to restore an error {@code ResultVoid} to a success.
@@ -66,9 +67,10 @@ public interface ResultVoid extends BaseResult {
      * success value. When this is an error, then nothing happens.</p>
      *
      * @param runnable the call if the Result is a success
+     * @return the original ResultVoid
      */
     @API(status = STABLE)
-    void onSuccess(Runnable runnable);
+    ResultVoid onSuccess(Runnable runnable);
 
     /**
      * A handler for error state, when the error matches the errorClass.

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

@@ -24,7 +24,6 @@ package net.kemitix.mon.result;
 import lombok.RequiredArgsConstructor;
 
 import java.util.Objects;
-import java.util.concurrent.Callable;
 import java.util.function.BinaryOperator;
 import java.util.function.Consumer;
 import java.util.function.Function;
@@ -62,8 +61,9 @@ class Success<T> implements Result<T> {
     }
 
     @Override
-    public void match(final Consumer<T> onSuccess, final Consumer<Throwable> onError) {
+    public Result<T> match(final Consumer<T> onSuccess, final Consumer<Throwable> onError) {
         onSuccess.accept(value);
+        return this;
     }
 
     @Override
@@ -93,8 +93,9 @@ class Success<T> implements Result<T> {
     }
 
     @Override
-    public void onSuccess(final Consumer<T> successConsumer) {
+    public Result<T> onSuccess(final Consumer<T> successConsumer) {
         successConsumer.accept(value);
+        return this;
     }
 
     @Override
@@ -110,11 +111,6 @@ class Success<T> implements Result<T> {
         return this;
     }
 
-    @Override
-    public <R> Result<R> andThen(final Function<T, Callable<R>> f) {
-        return result(f.apply(value));
-    }
-
     @Override
     public Result<T> thenWith(final Function<T, WithResultContinuation<T>> f) {
         return f.apply(value).call(this);

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

@@ -37,8 +37,9 @@ public class SuccessVoid implements ResultVoid {
     }
 
     @Override
-    public void match(final Runnable onSuccess, final Consumer<Throwable> onError) {
+    public ResultVoid match(final Runnable onSuccess, final Consumer<Throwable> onError) {
         onSuccess.run();
+        return this;
     }
 
     @Override
@@ -47,8 +48,9 @@ public class SuccessVoid implements ResultVoid {
     }
 
     @Override
-    public void onSuccess(final Runnable runnable) {
+    public ResultVoid onSuccess(final Runnable runnable) {
         runnable.run();
+        return this;
     }
 
     @Override

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

@@ -209,7 +209,7 @@ class EitherTest implements WithAssertions {
     }
     @Nested @DisplayName("getLeft") public class GetLeft {
         @Test
-        @DisplayName("")
+        @DisplayName("when is a Left then get the value")
         public void whenLeft_thenGetValue() {
             //given
             Either<String, Integer> either = Either.left("value");
@@ -220,7 +220,7 @@ class EitherTest implements WithAssertions {
         }
 
         @Test
-        @DisplayName("")
+        @DisplayName("when is a Right then is empty")
         public void whenRight_thenGetEmpty() {
             //given
             Either<Integer, String> either = Either.right("value");
@@ -232,7 +232,7 @@ class EitherTest implements WithAssertions {
     }
     @Nested @DisplayName("getRight") public class GetRight {
         @Test
-        @DisplayName("")
+        @DisplayName("when is a Left then is empty")
         public void whenLeft_thenGetEmpty() {
             //given
             Either<String, Integer> either = Either.left("value");
@@ -243,7 +243,7 @@ class EitherTest implements WithAssertions {
         }
 
         @Test
-        @DisplayName("")
+        @DisplayName("when is a Right then get the value")
         public void whenRight_thenGetValue() {
             //given
             Either<Integer, String> either = Either.right("value");

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

@@ -0,0 +1,110 @@
+package net.kemitix.mon;
+
+import net.kemitix.mon.reader.Reader;
+import org.assertj.core.api.WithAssertions;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.function.Function;
+
+public class ReaderTest
+        implements WithAssertions {
+
+    @Test
+    @DisplayName("read a value and return it")
+    void readAndReturn() {
+        //given
+        Integer value = 123;
+        Environment env = new Environment() {
+            @Override
+            public Integer intValue() {
+                return value;
+            }
+        };
+        Reader<Environment, Integer> program = (Environment e) -> {
+            return e.intValue();
+        };
+
+        //when
+        Integer result = program.run(env);
+
+        //then
+        assertThat(result).isEqualTo(value);
+    }
+
+    @Test
+    @DisplayName("map")
+    void map() {
+        //given
+        AtomicInteger value = new AtomicInteger(123);
+        Environment env = new Environment() {
+            @Override
+            public Integer intValue() {
+                return value.incrementAndGet();
+            }
+        };
+        Reader<Environment, String> program =
+                ((Reader<Environment, Integer>) e -> e.intValue())
+                        .map(i -> i * 2)
+                        .map(i -> Integer.toString(i));
+        //when
+        String result = program.run(env);
+        //then
+        assertThat(result).isEqualTo("248");// (123 + 1) * 2
+    }
+
+    @Test
+    @DisplayName("andThen")
+    void andThen() {
+        //given
+        AtomicInteger value = new AtomicInteger(123);
+        Environment env = new Environment() {
+            @Override
+            public Integer intValue() {
+                return value.incrementAndGet();
+            }
+        };
+        Reader<Environment, String> program =
+                ((Reader<Environment, Integer>) e -> e.intValue())
+                        .flatMap((e, i) -> e.intValue() + (i * 2))
+                        .flatMap((e, i) -> String.format("%.2f",
+                                i.floatValue() / e.intValue()));
+        //when
+        String result = program.run(env);
+        //then
+        assertThat(result).isEqualTo("2.96");// ((123 * 2) + (123 + 1)) / (123 + 2)
+    }
+
+    @Test
+    @DisplayName("flatMap")
+    void flatMap() {
+        //given
+        AtomicInteger value = new AtomicInteger(123);
+        Environment env = new Environment() {
+            @Override
+            public Integer intValue() {
+                return value.incrementAndGet();
+            }
+        };
+        Function<Integer, Reader<Environment, Integer>> addNextValue =
+                integer -> (Reader<Environment, Integer>) e -> e.intValue() + integer;
+        Function<Integer, Reader<Environment, Float>> divideByNextValue =
+                integer -> (Reader<Environment, Float>) e -> integer.floatValue() / e.intValue();
+        Reader<Environment, String> program =
+                ((Reader<Environment, Integer>) e -> e.intValue())
+                        .flatMap(addNextValue)
+                        .flatMap(divideByNextValue)
+                        .map(f -> String.format("%.3f", f));
+        //when
+        String result = program.run(env);
+        //then
+        assertThat(result).isEqualTo("1.976");// (123 + 124) / 125
+    }
+
+    private interface Environment {
+
+        Integer intValue();
+
+    }
+}

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

@@ -106,17 +106,6 @@ class ResultTest implements WithAssertions {
             assertThat(result.isError()).isFalse();
         }
 
-        @Test
-        void whenOkayVoid_match_isNull() {
-            //when
-            var result = Result.ok();
-            //then
-            result.match(
-                    () -> assertThat(true).isTrue(),
-                    error -> fail("not an error")
-            );
-        }
-
         @Test
         void whenOk_isOkay() {
             //when
@@ -133,17 +122,6 @@ class ResultTest implements WithAssertions {
             assertThat(result.isError()).isFalse();
         }
 
-        @Test
-        void whenOkay_matchSuccess() {
-            //given
-            final Result<String> result = Result.ok("good");
-            //then
-            result.match(
-                    success -> assertThat(success).isEqualTo("good"),
-                    error -> fail("not an error")
-            );
-        }
-
         @Test
         void whenError_isError() {
             //when
@@ -160,17 +138,6 @@ class ResultTest implements WithAssertions {
             assertThat(result.isError()).isTrue();
         }
 
-        @Test
-        void whenError_matchError() {
-            //given
-            final Result<Integer> result = anError(new Exception("bad"));
-            //then
-            result.match(
-                    success -> fail("not a success"),
-                    error -> assertThat(error.getMessage()).isEqualTo("bad")
-            );
-        }
-
         @Test
         void okay_toString() {
             //given
@@ -245,6 +212,95 @@ class ResultTest implements WithAssertions {
                 .flatMap(s -> Result.of(() -> {throw e;}));
     }
 
+    @Nested
+    @DisplayName("match")
+    class MatchTests {
+
+        @Test
+        void whenOkay_matchSuccess() {
+            //given
+            Result<String> ok = Result.ok("good");
+            //then
+            ok.match(
+                    success -> assertThat(success).isEqualTo("good"),
+                    error -> fail("not an error")
+            );
+        }
+
+        @Test
+        void whenError_matchError() {
+            //given
+            Result<Integer> error = anError(new Exception("bad"));
+            //then
+            error.match(
+                    success -> fail("not a success"),
+                    e -> assertThat(e.getMessage()).isEqualTo("bad")
+            );
+        }
+
+        @Test
+        void whenOkayVoid_matchOkay() {
+            //when
+            var ok = Result.ok();
+            //then
+            ok.match(
+                    () -> assertThat(true).isTrue(),
+                    error -> fail("not an error")
+            );
+        }
+
+        @Test
+        void whenErrorVoid_matchError() {
+            //when
+            var error = Result.error(new RuntimeException());
+            //then
+            error.match(
+                    () -> fail("not a success"),
+                    e -> assertThat(true).isTrue()
+            );
+        }
+
+        @Test
+        void whenOkay_match_returnsSelf() {
+            //given
+            final Result<String> ok = Result.ok("good");
+            //when
+            Result<String> result = ok.match(s -> {}, e -> {});
+            //then
+            assertThat(result).isSameAs(ok);
+        }
+
+        @Test
+        void whenError_match_returnsSelf() {
+            //given
+            final Result<Integer> error = anError(new Exception("bad"));
+            //then
+            Result<Integer> result = error.match(s -> {}, e -> {});
+            //then
+            assertThat(result).isSameAs(error);
+        }
+
+        @Test
+        void whenOkayVoid_match_returnsSelf() {
+            //given
+            ResultVoid ok = Result.ok();
+            //when
+            ResultVoid result = ok.match(() -> {}, e -> {});
+            //then
+            assertThat(result).isSameAs(ok);
+        }
+
+        @Test
+        void whenErrorVoid_match_returnsSelf() {
+            //given
+            ResultVoid error = Result.error(new RuntimeException());
+            //when
+            ResultVoid result = error.match(() -> {}, e -> {});
+            //then
+            assertThat(result).isSameAs(error);
+        }
+    }
+
     @Nested
     @DisplayName("flatMap")
     class FlatMapTests {
@@ -527,50 +583,6 @@ class ResultTest implements WithAssertions {
         }
     }
 
-    @Nested
-    @DisplayName("invert")
-    class InvertTests {
-        @Test
-        void justOkay_whenInvert_thenOkayJust() {
-            //given
-            final Maybe<Result<Integer>> justSuccess = Maybe.just(Result.ok(1));
-            //when
-            final Result<Maybe<Integer>> result = Result.swap(justSuccess);
-            //then
-            result.match(
-                    success -> assertThat(success.toOptional()).contains(1),
-                    error -> fail("Not an error")
-            );
-        }
-
-        @Test
-        void JustError_whenInvert_isError() {
-            //given
-            final RuntimeException exception = new RuntimeException();
-            final Maybe<Result<Integer>> justError = Maybe.just(anError(exception));
-            //when
-            final Result<Maybe<Integer>> result = Result.swap(justError);
-            //then
-            result.match(
-                    success -> fail("Not a success"),
-                    error -> assertThat(error).isSameAs(exception)
-            );
-        }
-
-        @Test
-        void nothing_whenInvert_thenOkayNothing() {
-            //given
-            final Maybe<Result<Integer>> nothing = Maybe.nothing();
-            //when
-            final Result<Maybe<Integer>> result = Result.swap(nothing);
-            //then
-            result.match(
-                    success -> assertThat(success.toOptional()).isEmpty(),
-                    error -> fail("Not an error")
-            );
-        }
-    }
-
     @Nested
     @DisplayName("use cases")
     class UseCaseTests {
@@ -832,6 +844,52 @@ class ResultTest implements WithAssertions {
             //then
             assertThat(capture).hasValue(1);
         }
+
+        @Test
+        void error_whenOnSuccess_returnsSelf() {
+            //given
+            final Result<Integer> error = anError(new RuntimeException());
+
+            //when
+            final Result<Integer> result = error.onSuccess(x -> {});
+
+            //then
+            assertThat(result).isSameAs(error);
+        }
+
+        @Test
+        void success_whenOnSuccess_returnsSelf() {
+            //given
+            final Result<Integer> ok = Result.ok(1);
+
+            //when
+            final Result<Integer> result = ok.onSuccess(x -> {});
+
+            //then
+            assertThat(result).isSameAs(ok);
+        }
+
+        @Test void errorVoid_whenOnSuccess_returnsSelf() {
+            //given
+            final ResultVoid error = Result.error(new RuntimeException());
+
+            //when
+            final ResultVoid result = error.onSuccess(() -> {});
+
+            //then
+            assertThat(result).isSameAs(error);
+        }
+
+        @Test void successVoid_whenOnSuccess_returnsSelf() {
+            //given
+            final ResultVoid ok = Result.ok();
+
+            //when
+            final ResultVoid result = ok.onSuccess(() -> {});
+
+            //then
+            assertThat(result).isSameAs(ok);
+        }
     }
 
     @Nested
@@ -957,122 +1015,6 @@ class ResultTest implements WithAssertions {
 
     }
 
-    @Nested
-    @DisplayName("andThen")
-    class AndThenTests {
-        @Test
-        void okay_whenAndThen_whereSuccess_isUpdatedSuccess() {
-            //given
-            final Result<Integer> ok = Result.ok(1);
-            //when
-            final Result<String> result = ok.andThen(v -> () -> "success");
-            //then
-            result.match(
-                    v -> assertThat(v).isEqualTo("success"),
-                    e -> fail("not an error"));
-        }
-
-        @Test
-        void okay_whenAndThen_whereError_isError() {
-            //given
-            final Result<Integer> ok = Result.ok(1);
-            final RuntimeException exception = new RuntimeException();
-            //when
-            final Result<Object> result = ok.andThen(v -> () -> {
-                throw exception;
-            });
-            //then
-            result.match(
-                    x -> fail("not a success"),
-                    e -> assertThat(e).isSameAs(exception));
-        }
-
-        @Test
-        void error_whereAndThen_whereSuccess_isError() {
-            //given
-            final RuntimeException exception = new RuntimeException();
-            final Result<Integer> error = anError(exception);
-            //when
-            final Result<Object> result = error.andThen(v -> () -> "success");
-            //then
-            result.match(
-                    x -> fail("not a success"),
-                    e -> assertThat(e).isSameAs(exception));
-        }
-
-        @Test
-        void error_whenAndThen_whereError_isOriginalError() {
-            //given
-            final RuntimeException exception1 = new RuntimeException();
-            final Result<Integer> error = anError(exception1);
-            //when
-            final Result<Object> result = error.andThen(v -> () -> {
-                throw new RuntimeException();
-            });
-            //then
-            result.match(
-                    x -> fail("not a success"),
-                    e -> assertThat(e).isSameAs(exception1));
-        }
-
-        @Test
-        void okayVoid_whenAndThen_whereSuccess_isUpdatedSuccess() {
-            //given
-            final ResultVoid ok = Result.ok();
-            //when
-            final ResultVoid result = ok.andThen(() -> {
-                // do nothing
-            });
-            //then
-            assertThat(result.isOkay()).isTrue();
-        }
-
-        @Test
-        void okayVoid_whenAndThen_whereError_isError() {
-            //given
-            final ResultVoid ok = Result.ok();
-            final RuntimeException exception = new RuntimeException();
-            //when
-            final ResultVoid result = ok.andThen(() -> {
-                throw exception;
-            });
-            //then
-            result.match(
-                    () -> fail("not a success"),
-                    e -> assertThat(e).isSameAs(exception));
-        }
-
-        @Test
-        void errorVoid_whereAndThen_whereSuccess_isError() {
-            //given
-            final RuntimeException exception = new RuntimeException();
-            final ResultVoid error = Result.error(exception);
-            //when
-            final ResultVoid result = error.andThen(() -> {
-                // do nothing
-            });
-            //then
-            result.match(
-                    () -> fail("not a success"),
-                    e -> assertThat(e).isSameAs(exception));
-        }
-
-        @Test
-        void errorVoid_whenAndThen_whereError_isOriginalError() {
-            //given
-            final RuntimeException exception1 = new RuntimeException();
-            final ResultVoid error = Result.error(exception1);
-            //when
-            final ResultVoid result = error.andThen(() -> {
-                throw new RuntimeException();
-            });
-            //then
-            result.match(
-                    () -> fail("not a success"),
-                    e -> assertThat(e).isSameAs(exception1));
-        }
-    }
-
     @Nested
     @DisplayName("thenWith")
     class ThenWithTests {
@@ -1668,6 +1610,64 @@ class ResultTest implements WithAssertions {
 
     }
 
+    @Nested
+    @DisplayName("andThen")
+    class AndThenTests {
+
+        @Test
+        void successVoid_andThen_returnSelf() {
+            //given
+            ResultVoid ok = Result.ok();
+            //when
+            ResultVoid result = ok.andThen(() -> {});
+            //then
+            assertThat(result).isSameAs(ok);
+        }
+
+        @Test
+        void successVoid_andThen_isCalled() {
+            //given
+            ResultVoid ok = Result.ok();
+            AtomicBoolean called = new AtomicBoolean(false);
+            //when
+            ok.andThen(() -> called.set(true));
+            //then
+            assertThat(called).isTrue();
+        }
+
+        @Test
+        void successVoid_andThen_exception_errorVoid() {
+            //given
+            ResultVoid ok = Result.ok();
+            //when
+            ResultVoid result = ok.andThen(() -> {throw new RuntimeException();});
+            //then
+            assertThat(result.isError()).isTrue();
+        }
+
+        @Test
+        void errorVoid_andThen_returnsSelf() {
+            //given
+            ResultVoid error = Result.error(new RuntimeException());
+            //when
+            ResultVoid result = error.andThen(() -> {});
+            //then
+            assertThat(result).isSameAs(error);
+        }
+
+        @Test
+        void errorVoid_andThen_notCalled() {
+            //given
+            ResultVoid error = Result.error(new RuntimeException());
+            final AtomicBoolean called = new AtomicBoolean(false);
+            //when
+            error.andThen(() -> called.set(true));
+            //then
+            assertThat(called).isFalse();
+        }
+
+    }
+
     /**
      * These include snippets from the Javadocs and are meant to prove that the examples are valid.
      */
@@ -2293,7 +2293,7 @@ class ResultTest implements WithAssertions {
 
         Result<Double> businessOperation(final String fileName1, final String fileName2) {
             return readIntFromFile(fileName1)
-                    .andThen(intFromFile1 -> () -> adjustValue(intFromFile1))
+                    .map(this::adjustValue)
                     .flatMap(adjustedIntFromFile1 -> readIntFromFile(fileName2)
                             .flatMap(intFromFile2 -> adjustedIntFromFile1
                                     .flatMap(aif1 -> calculateAverage(aif1, intFromFile2))));

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

@@ -1,10 +1,7 @@
 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;
 
@@ -18,8 +15,6 @@ class WrapperTest {
 
     interface WrappedIterableString extends Wrapper<Iterable<String>> { }
 
-    interface WrappedListInteger extends Wrapper<List<Integer>> {}
-
     interface AWrapper extends Wrapper<String> {}
 
     @Test
@@ -65,6 +60,7 @@ class WrapperTest {
         final WrappedString wrappedString = () -> "1";
         final WrappedInteger wrappedInteger = () -> 1;
         //then
+        //noinspection AssertBetweenInconvertibleTypes
         assertThat(wrappedString).isNotEqualTo(wrappedInteger);
     }