Add pricing property tests

pom.xml

@@ -52,6 +52,31 @@
       <artifactId>mysql-connector-j</artifactId>
       <version>8.4.0</version>
     </dependency>
+    <!-- Test dependencies -->
+    <dependency>
+      <groupId>org.junit.jupiter</groupId>
+      <artifactId>junit-jupiter</artifactId>
+      <version>5.10.2</version>
+      <scope>test</scope>
+    </dependency>
+    <dependency>
+      <groupId>net.jqwik</groupId>
+      <artifactId>jqwik</artifactId>
+      <version>1.8.2</version>
+      <scope>test</scope>
+    </dependency>
+    <dependency>
+      <groupId>com.github.seeseemelk</groupId>
+      <artifactId>MockBukkit-v1.20</artifactId>
+      <version>3.14.0</version>
+      <scope>test</scope>
+    </dependency>
+    <dependency>
+      <groupId>org.mockito</groupId>
+      <artifactId>mockito-core</artifactId>
+      <version>5.11.0</version>
+      <scope>test</scope>
+    </dependency>
   </dependencies>
 
   <build>
@@ -80,6 +105,14 @@
           </execution>
         </executions>
       </plugin>
+      <plugin>
+        <groupId>org.apache.maven.plugins</groupId>
+        <artifactId>maven-surefire-plugin</artifactId>
+        <version>3.1.2</version>
+        <configuration>
+          <useModulePath>false</useModulePath>
+        </configuration>
+      </plugin>
     </plugins>
   </build>
 </project>

src/test/java/com/yourorg/servershop/dynamic/PricingPropertiesTest.java

@@ -0,0 +1,107 @@
+package com.yourorg.servershop.dynamic;
+
+import be.seeseemelk.mockbukkit.MockBukkit;
+import be.seeseemelk.mockbukkit.ServerMock;
+import net.jqwik.api.*;
+import org.bukkit.Material;
+import org.bukkit.OfflinePlayer;
+import org.bukkit.plugin.Plugin;
+import org.bukkit.plugin.ServicePriority;
+import org.junit.jupiter.api.AfterAll;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Assertions;
+
+import com.yourorg.servershop.ServerShopPlugin;
+import com.yourorg.servershop.shop.ItemEntry;
+
+import net.milkbowl.vault.economy.Economy;
+import net.milkbowl.vault.economy.EconomyResponse;
+
+import org.mockito.Mockito;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.ArgumentMatchers.anyDouble;
+
+import java.lang.reflect.Field;
+import java.util.Map;
+
+public class PricingPropertiesTest {
+    static ServerMock server;
+    static ServerShopPlugin plugin;
+
+    @BeforeAll
+    static void init() {
+        server = MockBukkit.mock();
+        Plugin vault = MockBukkit.createMockPlugin("Vault");
+        Economy econ = Mockito.mock(Economy.class, Mockito.RETURNS_DEEP_STUBS);
+        Mockito.when(econ.withdrawPlayer(any(OfflinePlayer.class), anyDouble()))
+                .thenReturn(new EconomyResponse(0, 0, EconomyResponse.ResponseType.SUCCESS, ""));
+        Mockito.when(econ.depositPlayer(any(OfflinePlayer.class), anyDouble()))
+                .thenReturn(new EconomyResponse(0, 0, EconomyResponse.ResponseType.SUCCESS, ""));
+        Mockito.when(econ.getBalance(any(OfflinePlayer.class))).thenReturn(1_000_000.0);
+        server.getServicesManager().register(Economy.class, econ, vault, ServicePriority.Normal);
+        plugin = MockBukkit.load(ServerShopPlugin.class);
+    }
+
+    @AfterAll
+    static void shutdown() {
+        MockBukkit.unmock();
+    }
+
+    @Provide
+    Arbitrary<Material> materials() {
+        return Arbitraries.of(plugin.catalog().allMaterials());
+    }
+
+    @Provide
+    Arbitrary<Integer> counts() {
+        return Arbitraries.integers().between(1, 10_000);
+    }
+
+    @Property
+    void priceWithinBounds(@ForAll("materials") Material mat) {
+        ItemEntry entry = plugin.catalog().get(mat).orElseThrow();
+        DynamicPricingManager mgr = new DynamicPricingManager(plugin);
+        double buy = mgr.buyPrice(mat, entry.buyPrice());
+        double sell = mgr.sellPrice(mat, entry.sellPrice());
+
+        double minBuy = Math.max(0.01, entry.buyPrice() * plugin.getConfig().getDouble("priceModel.minFactor"));
+        double maxBuy = Math.max(minBuy, entry.buyPrice() * plugin.getConfig().getDouble("priceModel.maxFactor"));
+        Assertions.assertTrue(buy >= minBuy && buy <= maxBuy);
+
+        double minSell = Math.max(0.01, entry.sellPrice() * plugin.getConfig().getDouble("priceModel.minFactor"));
+        double maxSell = Math.max(minSell, entry.sellPrice() * plugin.getConfig().getDouble("priceModel.maxFactor"));
+        Assertions.assertTrue(sell >= minSell && sell <= maxSell);
+    }
+
+    @Property
+    void spreadRespected(@ForAll("materials") Material mat) {
+        ItemEntry entry = plugin.catalog().get(mat).orElseThrow();
+        DynamicPricingManager mgr = new DynamicPricingManager(plugin);
+        double buy = mgr.buyPrice(mat, entry.buyPrice());
+        double sell = mgr.sellPrice(mat, entry.sellPrice());
+        Assertions.assertTrue(buy >= sell);
+    }
+
+    @Property
+    void adjustmentsCapped(@ForAll("materials") Material mat,
+                           @ForAll("counts") int buyQty,
+                           @ForAll("counts") int sellQty) throws Exception {
+        DynamicPricingManager mgr = new DynamicPricingManager(plugin);
+        Map<Material, PriceState> map = stateMap(mgr);
+        mgr.adjustOnBuy(mat, buyQty);
+        double maxMult = plugin.getConfig().getDouble("dynamicPricing.maxMultiplier");
+        double minMult = plugin.getConfig().getDouble("dynamicPricing.minMultiplier");
+        double afterBuy = map.get(mat).multiplier;
+        Assertions.assertTrue(afterBuy <= maxMult);
+        mgr.adjustOnSell(mat, sellQty);
+        double afterSell = map.get(mat).multiplier;
+        Assertions.assertTrue(afterSell >= minMult && afterSell <= maxMult);
+    }
+
+    @SuppressWarnings("unchecked")
+    private static Map<Material, PriceState> stateMap(DynamicPricingManager mgr) throws Exception {
+        Field f = DynamicPricingManager.class.getDeclaredField("map");
+        f.setAccessible(true);
+        return (Map<Material, PriceState>) f.get(mgr);
+    }
+}