add new package

patterns-modules/idd/README.md

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+### Relevant Articles:
+- [Introduction to Interface Driven Development (IDD)](https://www.baeldung.com/java-idd)

patterns-modules/idd/pom.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <artifactId>idd</artifactId>
+    <version>1.0</version>
+    <name>idd</name>
+    <packaging>jar</packaging>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>patterns-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+    </parent>
+
+</project>

patterns-modules/idd/src/main/java/com/baeldung/idd/CreateHelpRequestDTO.java

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+package com.baeldung.idd;
+
+public class CreateHelpRequestDTO {
+
+    private final HelpRequestStatus status;
+
+    public CreateHelpRequestDTO(HelpRequestStatus status) {
+        this.status = status;
+    }
+
+    public HelpRequestStatus getStatus() {
+        return status;
+    }
+
+}

patterns-modules/idd/src/main/java/com/baeldung/idd/HelpRequestDTO.java

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+package com.baeldung.idd;
+
+public class HelpRequestDTO {
+    private HelpRequestStatus status;
+
+    public HelpRequestStatus getStatus() {
+        return status;
+    }
+
+    public HelpRequestDTO(HelpRequestStatus status) {
+        this.status = status;
+    }
+}

patterns-modules/idd/src/main/java/com/baeldung/idd/HelpRequestService.java

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+package com.baeldung.idd;
+
+import java.util.List;
+
+public interface HelpRequestService {
+    HelpRequestDTO createHelpRequest(CreateHelpRequestDTO createHelpRequestDTO);
+
+    List<HelpRequestDTO> findAllByStatus(HelpRequestStatus status);
+
+    HelpRequestDTO updateHelpRequest(UpdateHelpRequestDTO updateHelpRequestDTO);
+}

patterns-modules/idd/src/main/java/com/baeldung/idd/HelpRequestServiceImpl.java

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+package com.baeldung.idd;
+
+import java.util.List;
+
+public class HelpRequestServiceImpl implements HelpRequestService {
+
+    @Override
+    public HelpRequestDTO createHelpRequest(CreateHelpRequestDTO createHelpRequestDTO) {
+        // here goes the implementation
+        return new HelpRequestDTO(createHelpRequestDTO.getStatus());
+    }
+
+    @Override
+    public List<HelpRequestDTO> findAllByStatus(HelpRequestStatus status) {
+        // here goes the implementation
+        return List.of(new HelpRequestDTO(status), new HelpRequestDTO(status));
+    }
+
+    @Override
+    public HelpRequestDTO updateHelpRequest(UpdateHelpRequestDTO updateHelpRequestDTO) {
+        // here goes the implementation
+        return new HelpRequestDTO(updateHelpRequestDTO.getStatus());
+    }
+}

patterns-modules/idd/src/main/java/com/baeldung/idd/HelpRequestStatus.java

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+package com.baeldung.idd;
+
+public enum HelpRequestStatus {
+    OPEN, IN_PROGRESS, CLOSED
+}
+

patterns-modules/idd/src/main/java/com/baeldung/idd/UpdateHelpRequestDTO.java

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+package com.baeldung.idd;
+
+public class UpdateHelpRequestDTO {
+
+    private final HelpRequestStatus status;
+
+    public UpdateHelpRequestDTO(HelpRequestStatus status) {
+        this.status = status;
+    }
+
+    public HelpRequestStatus getStatus() {
+        return status;
+    }
+}

patterns-modules/idd/src/test/java/com/baeldung/idd/HelpRequestServiceUnitTest.java

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+package com.baeldung.idd;
+
+import org.assertj.core.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+import java.util.List;
+
+public class HelpRequestServiceUnitTest {
+
+    HelpRequestService testHelpRequestService = new HelpRequestService() {
+        @Override
+        public HelpRequestDTO createHelpRequest(CreateHelpRequestDTO createHelpRequestDTO) {
+            return new HelpRequestDTO(HelpRequestStatus.OPEN);
+        }
+
+        @Override
+        public List<HelpRequestDTO> findAllByStatus(HelpRequestStatus status) {
+            return List.of(new HelpRequestDTO(HelpRequestStatus.OPEN));
+        }
+
+        @Override
+        public HelpRequestDTO updateHelpRequest(UpdateHelpRequestDTO updateHelpRequestDTO) {
+            return new HelpRequestDTO(HelpRequestStatus.OPEN);
+        }
+    };
+
+    @Test
+    public void givenHelpRequest_whenCreateHelpRequest_thenHelpRequestIsCreated() {
+        // given
+        CreateHelpRequestDTO createHelpRequestDTO = new CreateHelpRequestDTO(HelpRequestStatus.OPEN);
+
+        // when
+        HelpRequestDTO helpRequestDTO = testHelpRequestService.createHelpRequest(createHelpRequestDTO);
+
+        // then
+        Assertions.assertThat(helpRequestDTO).isNotNull();
+        Assertions.assertThat(helpRequestDTO.getStatus()).isEqualTo(HelpRequestStatus.OPEN);
+    }
+
+    @Test
+    public void givenHelpRequestList_whenFindAllByStatus_shouldContainOnlyStatus() {
+        HelpRequestService helpRequestService = new HelpRequestServiceImpl();
+        List<HelpRequestDTO> allByStatusOpen = helpRequestService.findAllByStatus(HelpRequestStatus.OPEN);
+        Assertions.assertThat(allByStatusOpen).extracting(HelpRequestDTO::getStatus).containsOnly(HelpRequestStatus.OPEN);
+    }
+
+}