コンストラクタで逆順の生成を抑止する

Author: irof

jig-core/src/main/java/org/dddjava/jig/domain/model/information/relation/graph/MutualEdge.java

@@ -9,6 +9,12 @@
  */
 public record MutualEdge<NODE>(NODE a, NODE b) implements Comparable<MutualEdge<NODE>> {
 
+    public MutualEdge {
+        if (a.toString().compareTo(b.toString()) > 0) {
+            throw new IllegalArgumentException("順序が a <= b でない");
+        }
+    }
+
     public static <T> MutualEdge<T> from(Edge<T> edge) {
         var a = edge.from();
         var b = edge.to();

jig-core/src/test/java/org/dddjava/jig/domain/model/information/relation/graph/MutualEdgeTest.java

@@ -0,0 +1,39 @@
+package org.dddjava.jig.domain.model.information.relation.graph;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class MutualEdgeTest {
+
+    @Test
+    void Edgeから生成できる() {
+        var actual = MutualEdge.from(new Edge<>("A", "B"));
+
+        assertEquals("A", actual.a());
+        assertEquals("B", actual.b());
+    }
+
+    @Test
+    void Edgeから生成できる_順番が入れ替わる() {
+        var actual = MutualEdge.from(new Edge<>("B", "A"));
+
+        assertEquals("A", actual.a());
+        assertEquals("B", actual.b());
+    }
+
+
+    @Test
+    void 逆順だと生成できない() {
+        assertThrows(IllegalArgumentException.class, () -> {
+            new MutualEdge<>("B", "A");
+        });
+    }
+
+    @Test
+    void 自己参照は生成できる() {
+        assertDoesNotThrow(() -> {
+            new MutualEdge<>("A", "A");
+        });
+    }
+}