issue #335 Monad pattern introduced

monad/src/test/java/com/iluwatar/monad/AppTest.java

@@ -0,0 +1,13 @@
+package com.iluwatar.monad;
+
+import org.junit.Test;
+
+public class AppTest {
+
+  @Test
+  public void testMain() {
+    String[] args = {};
+    App.main(args);
+  }
+
+}

monad/src/test/java/com/iluwatar/monad/MonadTest.java

@@ -0,0 +1,42 @@
+package com.iluwatar.monad;
+
+
+import junit.framework.Assert;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.ExpectedException;
+
+import java.util.Objects;
+
+public class MonadTest {
+
+  @Rule
+  public ExpectedException thrown = ExpectedException.none();
+
+  @Test
+  public void testForInvalidName() {
+    thrown.expect(IllegalStateException.class);
+    User tom = new User(null, 21, Sex.MALE, "tom@foo.bar");
+    Validator.of(tom).validate(User::getName, Objects::nonNull, "name cannot be null").get();
+  }
+
+  @Test
+  public void testForInvalidAge() {
+    thrown.expect(IllegalStateException.class);
+    User tom = new User("John", 17, Sex.MALE, "john@qwe.bar");
+    Validator.of(tom).validate(User::getName, Objects::nonNull, "name cannot be null")
+        .validate(User::getAge, age -> age > 21, "user is underaged")
+        .get();
+  }
+
+  @Test
+  public void testForValid() {
+    User tom = new User("Sarah", 42, Sex.FEMALE, "sarah@det.org");
+    User validated = Validator.of(tom).validate(User::getName, Objects::nonNull, "name cannot be null")
+        .validate(User::getAge, age -> age > 21, "user is underaged")
+        .validate(User::getSex, sex -> sex == Sex.FEMALE, "user is not female")
+        .validate(User::getEmail, email -> email.contains("@"), "email does not contain @ sign")
+        .get();
+    Assert.assertSame(validated, tom);
+  }
+}