Add parameterized ShapeContractTest for Shape interface invariants

Verify clone(), getBounds(), and translate() contracts across all Shape
implementations (SRectangle, SCircle, STriangle, SText, SCollection)
using @ParameterizedTest + @MethodSource.

Also adds junit-jupiter-params dependency to pom.xml.

Closes #8

pom.xml

@@ -92,5 +92,12 @@
             <version>5.10.0</version>
             <scope>test</scope>
         </dependency>
+
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter-params</artifactId>
+            <version>5.10.0</version>
+            <scope>test</scope>
+        </dependency>
     </dependencies>
 </project>

src/test/java/ovh/gasser/newshapes/shapes/ShapeContractTest.java

@@ -0,0 +1,73 @@
+package ovh.gasser.newshapes.shapes;
+
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.MethodSource;
+
+import java.awt.Rectangle;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+/**
+ * Parameterized contract tests verifying Shape interface invariants
+ * across all implementations (SRectangle, SCircle, STriangle, SText, SCollection).
+ */
+class ShapeContractTest {
+
+    @ParameterizedTest(name = "{0}")
+    @MethodSource("ovh.gasser.newshapes.shapes.ShapeFactory#allShapes")
+    void cloneReturnsIndependentCopy(Shape shape) {
+        Shape cloned = shape.clone();
+
+        // clone must not be the same instance
+        assertNotSame(shape, cloned, "clone() must return a new instance");
+
+        // clone must have equal bounds
+        assertEquals(shape.getBounds(), cloned.getBounds(),
+                "clone() must preserve bounds");
+
+        // mutating the clone must not affect the original
+        Rectangle originalBounds = shape.getBounds();
+        cloned.translate(999, 999);
+        assertEquals(originalBounds, shape.getBounds(),
+                "Translating the clone must not affect the original's bounds");
+    }
+
+    @ParameterizedTest(name = "{0}")
+    @MethodSource("ovh.gasser.newshapes.shapes.ShapeFactory#allShapes")
+    void getBoundsReturnsCopy(Shape shape) {
+        Rectangle bounds1 = shape.getBounds();
+        Rectangle bounds2 = shape.getBounds();
+
+        // successive calls must return equal bounds
+        assertEquals(bounds1, bounds2,
+                "getBounds() must return consistent values");
+
+        // but not the same object (defensive copy)
+        assertNotSame(bounds1, bounds2,
+                "getBounds() must return a copy, not internal state");
+
+        // mutating the returned Rectangle must not affect the shape
+        bounds1.translate(500, 500);
+        assertEquals(bounds2, shape.getBounds(),
+                "Mutating the returned Rectangle must not affect the shape");
+    }
+
+    @ParameterizedTest(name = "{0}")
+    @MethodSource("ovh.gasser.newshapes.shapes.ShapeFactory#allShapes")
+    void translateMutatesInPlace(Shape shape) {
+        Rectangle before = shape.getBounds();
+        int dx = 7, dy = -3;
+
+        shape.translate(dx, dy);
+
+        Rectangle after = shape.getBounds();
+        assertEquals(before.x + dx, after.x,
+                "translate() must shift x by dx");
+        assertEquals(before.y + dy, after.y,
+                "translate() must shift y by dy");
+        assertEquals(before.width, after.width,
+                "translate() must not change width");
+        assertEquals(before.height, after.height,
+                "translate() must not change height");
+    }
+}

src/test/java/ovh/gasser/newshapes/shapes/ShapeFactory.java

@@ -0,0 +1,25 @@
+package ovh.gasser.newshapes.shapes;
+
+import java.awt.Color;
+import java.util.stream.Stream;
+
+/**
+ * Provides Shape instances for parameterized contract tests.
+ */
+public final class ShapeFactory {
+
+    private ShapeFactory() {}
+
+    static Stream<Shape> allShapes() {
+        return Stream.of(
+                SRectangle.create(10, 20, 100, 50),
+                SCircle.create(5, 5, 30),
+                STriangle.create(0, 0, 40, Color.RED, Color.BLACK),
+                SText.create(15, 25, "Hello"),
+                SCollection.of(
+                        SRectangle.create(0, 0, 20, 20),
+                        SCircle.create(10, 10, 5)
+                )
+        );
+    }
+}