test: Generic contracts are run only on **.testclasses.** (#2716)

src/main/java/spoon/support/visitor/java/JavaReflectionTreeBuilder.java

@@ -210,6 +210,7 @@ public void addMethod(CtMethod ctMethod) {
 				field.setSimpleName(ctMethod.getSimpleName());
 				field.setModifiers(ctMethod.getModifiers());
 				field.setType(ctMethod.getType());
+				field.setShadow(true);
 				ctAnnotationType.addMethod(field);
 			}
 		});

src/main/java/spoon/testing/utils/Check.java

@@ -25,13 +25,18 @@ private Check() {
 		throw new AssertionError();
 	}
 
-	public static <T> T assertNotNull(T reference) {
+	/** throws AssertionError if "reference" is null */
+	public static <T> T assertNotNull(String msg, T reference) {
 		if (reference == null) {
-			throw new AssertionError("Your parameter can't be null.");
+			throw new AssertionError(msg);
 		}
 		return reference;
 	}
 
+	public static <T> T assertNotNull(T reference) {
+		return assertNotNull("Your parameter can't be null.", reference);
+	}
+
 	public static <T extends File> T assertExists(T file) {
 		if (!file.exists()) {
 			throw new AssertionError("You should specify an existing file.");

src/test/java/spoon/test/executable/ExecutableTest.java

@@ -17,6 +17,7 @@
 package spoon.test.executable;
 
 import org.junit.Test;
+import spoon.ContractVerifier;
 import spoon.Launcher;
 import spoon.reflect.CtModel;
 import spoon.reflect.code.CtBlock;
@@ -124,6 +125,6 @@ public void testShadowValueOf() {
 
 		assertEquals(valueOf, shadowValueOf);
 		assertEquals(valueOf.getDeclaration(), shadowValueOf.getDeclaration());
-		MainTest.checkShadow(shadowValueOf.getParent(CtPackage.class));
+		new ContractVerifier(shadowValueOf.getParent(CtPackage.class)).checkShadow();
 	}
 }

src/test/java/spoon/test/generics/GenericsTest.java

@@ -17,6 +17,7 @@
 package spoon.test.generics;
 
 import org.junit.Test;
+import spoon.ContractVerifier;
 import spoon.Launcher;
 import spoon.SpoonModelBuilder;
 import spoon.compiler.SpoonResourceHelper;
@@ -1435,9 +1436,9 @@ public void testIsGenericTypeEqual() {
 		 */
 		assertEquals(adaptedMethod.getParameters().get(0).getType(), classGetter.getType());
 		assertEquals(adaptedMethod.getParameters().get(0).getType(), classSetter.getParameters().get(0).getType());
-		
-		MainTest.checkParentConsistency(launcher.getFactory().getModel().getRootPackage());
-		MainTest.checkParentConsistency(adaptedMethod);
+
+		new ContractVerifier(launcher.getFactory().getModel().getRootPackage()).checkParentConsistency();
+		new ContractVerifier().checkParentConsistency(adaptedMethod);
 	}
 
 	@Test