feat: Ladder 생성 유효성 검사 추가

Author: mjin1220

src/main/java/ladder/domain/Ladder.java

@@ -1,12 +1,16 @@
 package ladder.domain;
 
+import java.util.Objects;
+
 public class Ladder {
 
     private final Participants participants;
     private final LadderHeight height;
     private final Lines lines;
 
     public Ladder(final Participants participants, final LadderHeight height, final Lines lines) {
+        validateOrThrow(participants, height, lines);
+
         this.participants = participants;
         this.height = height;
         this.lines = lines;
@@ -28,4 +32,10 @@ public Line getLine(final int index) {
         return this.lines.getLines()
                          .get(index);
     }
+
+    private void validateOrThrow(final Participants participants, final LadderHeight height, final Lines lines) {
+        if (Objects.isNull(participants) || Objects.isNull(height) || Objects.isNull(lines)) {
+            throw new IllegalArgumentException("null인 멤버 변수를 포함할 수 없습니다.");
+        }
+    }
 }

src/test/java/ladder/domain/LadderHeightTest.java

@@ -3,6 +3,7 @@
 import org.junit.jupiter.api.DisplayName;
 import org.junit.jupiter.api.Test;
 
+import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.assertThatThrownBy;
 
 public class LadderHeightTest {
@@ -14,4 +15,11 @@ void invalid() {
                 .isInstanceOf(IllegalArgumentException.class)
                 .hasMessageContaining("유효하지 않은 사다리 높이입니다.");
     }
+
+    @DisplayName("생성")
+    @Test
+    void create() {
+        LadderHeight ladderHeight = new LadderHeight(7);
+        assertThat(ladderHeight).isEqualTo(new LadderHeight(7));
+    }
 }

src/test/java/ladder/domain/LadderTest.java

@@ -8,6 +8,8 @@
 import java.util.stream.Stream;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+import static org.junit.jupiter.api.Assertions.assertAll;
 
 public class LadderTest {
 
@@ -20,13 +22,30 @@ void create() {
         final LadderHeight ladderHeight = new LadderHeight(5);
         final Ladder ladder = new Ladder(participants, ladderHeight, new Lines(List.of(new Line(List.of(true)))));
 
-        assertThat(ladder.getParticipants()).isEqualTo(new Participants(Stream.of("woody", "jacob", "tate", "test")
-                                                                              .map(Participant::new)
-                                                                              .collect(Collectors.toList())));
-        assertThat(ladder.getParticipants()
-                         .size()).isEqualTo(4);
-        assertThat(ladder.getHeight()).isEqualTo(new LadderHeight(5));
-        assertThat(ladder.getLines()
-                         .size()).isEqualTo(1);
+        assertAll(
+                () -> assertThat(ladder.getParticipants()
+                                       .size()).isEqualTo(4),
+                () -> assertThat(ladder.getHeight()).isEqualTo(new LadderHeight(5)),
+                () -> assertThat(ladder.getLines()
+                                       .size()).isEqualTo(1)
+        );
+    }
+
+    @DisplayName("사다리 생성 실패")
+    @Test
+    void invalid() {
+        final Participants participants = new Participants(Stream.of("woody", "jacob", "tate", "test")
+                                                                 .map(Participant::new)
+                                                                 .collect(Collectors.toList()));
+        final LadderHeight ladderHeight = new LadderHeight(5);
+        final Ladder ladder = new Ladder(participants, ladderHeight, new Lines(List.of(new Line(List.of(true)))));
+
+        assertAll(
+                () -> assertThatThrownBy(() -> new Ladder(null, ladderHeight,
+                        new Lines(List.of(new Line(List.of(true)))))),
+                () -> assertThatThrownBy(() -> new Ladder(participants, null,
+                        new Lines(List.of(new Line(List.of(true)))))),
+                () -> assertThatThrownBy(() -> new Ladder(participants, ladderHeight, null))
+        );
     }
 }

src/test/java/ladder/domain/ParticipantsTest.java

@@ -4,7 +4,9 @@
 import org.junit.jupiter.api.Test;
 
 import java.util.Collections;
+import java.util.List;
 
+import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.assertThatThrownBy;
 
 public class ParticipantsTest {
@@ -16,4 +18,11 @@ void invalid() {
                 .isInstanceOf(IllegalArgumentException.class)
                 .hasMessageContaining("참가자는 최소 1명 이상이여야 합니다.");
     }
+
+    @DisplayName("생성")
+    @Test
+    void create() {
+        Participants participants = new Participants(List.of(new Participant("woody")));
+        assertThat(participants).isEqualTo(new Participants(List.of(new Participant("woody"))));
+    }
 }