Bugfix 2974 fix npe

src/main/java/org/mockito/internal/configuration/injection/filter/TypeBasedCandidateFilter.java

@@ -77,9 +77,15 @@ protected boolean isCompatibleTypes(Type typeToMock, Type mockType, Field inject
 
     private Stream<Type> getSuperTypes(Class<?> concreteMockClass) {
         Stream<Type> mockInterfaces = Arrays.stream(concreteMockClass.getGenericInterfaces());
-        Stream<Type> mockSuperTypes =
-                Stream.concat(mockInterfaces, Stream.of(concreteMockClass.getGenericSuperclass()));
-        return mockSuperTypes;
+        Type genericSuperclass = concreteMockClass.getGenericSuperclass();
+        // for java.lang.Object, genericSuperclass is null
+        if (genericSuperclass != null) {
+            Stream<Type> mockSuperTypes =
+                    Stream.concat(mockInterfaces, Stream.of(genericSuperclass));
+            return mockSuperTypes;
+        } else {
+            return mockInterfaces;
+        }
     }
 
     private boolean recurseOnTypeArguments(

subprojects/junit-jupiter/src/test/java/org/mockitousage/GenericTypeMockTest.java

@@ -8,13 +8,15 @@
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertNotNull;
 import static org.junit.jupiter.api.Assertions.assertNull;
+import static org.junit.jupiter.api.Assertions.assertSame;
 import static org.mockito.MockitoAnnotations.*;
 
 import java.sql.Time;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Date;
 import java.util.HashSet;
+import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
@@ -345,5 +347,30 @@ public void testMockExists() {
 
     }
 
+    /**
+     * Verify regression https://github.com/mockito/mockito/issues/2974 is fixed.
+     */
+    @Nested
+    public class RegressionNpe {
+        public abstract class Change {}
+        public class ChangeCollection<TChange extends Change> implements Iterable<TChange> {
+            private List<TChange> changes = new ArrayList<TChange>();
+            @Override
+            public Iterator<TChange> iterator() {
+                return null;
+            }
+        }
+
+        @Mock Change change0;
+
+        @InjectMocks ChangeCollection spiedImpl = new ChangeCollection();
+        @Mock(name = "changes") List<Change> innerList;
+
+        @Test
+        public void testNoNpe() {
+            assertSame(innerList, spiedImpl.changes);
+        }
+
+    }
 }