feat(model): Combination recipe record + order-independent key

Semesterprojekt/src/test/java/thb/jeanluc/adventure/model/CombinationTest.java

@@ -0,0 +1,28 @@
+package thb.jeanluc.adventure.model;
+
+import org.junit.jupiter.api.Test;
+
+import java.util.List;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class CombinationTest {
+
+    @Test
+    void keyIsOrderIndependentAndSorted() {
+        assertThat(Combination.key("matches", "torch"))
+                .isEqualTo(Combination.key("torch", "matches"))
+                .isEqualTo("matches|torch");
+        assertThat(Combination.key("b", "a")).isEqualTo("a|b");
+    }
+
+    @Test
+    void nullCollectionComponentsBecomeEmpty() {
+        Combination c = new Combination("a", "b", null, null, null, null, "ok", null);
+        assertThat(c.requires()).isEmpty();
+        assertThat(c.consume()).isEmpty();
+        assertThat(c.effects()).isEmpty();
+        assertThat(c.produce()).isNull();
+        assertThat(c.key()).isEqualTo("a|b");
+    }
+}