Add PurchaseTest

src/test/java/PurchaseTest.java

@@ -0,0 +1,37 @@
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.math.BigDecimal;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+public class PurchaseTest {
+    Stock stock;
+    Share share;
+    Purchase purchase;
+
+    @BeforeEach
+    void setUp() {
+        this.stock = new Stock("symbol", "company", new BigDecimal(100));
+        this.share = new Share(this.stock, new BigDecimal(20), new BigDecimal(50));
+        this.purchase = new Purchase(this.share, 18);
+    }
+
+    @Test
+    void commit_validPurchase_updatesPlayer() {
+
+        // Arrange
+        Player player = new Player("Jane", new BigDecimal(500000));
+        BigDecimal startingMoney = player.getMoney();
+
+        // Act
+        this.purchase.commit(player);
+
+        // Assert
+        assertEquals(1, startingMoney.subtract(player.getMoney()).signum());
+
+    }
+
+
+
+}