Default mock of Optional.isEmpty() returns true when using RETURN_DEE…

…P_STUBS ReturnsDeepStubs now answers with true on Optional.isEmpty() when using RETURN_DEEP_STUBS. But the User can still mock the methods of Optional. In the normal mock case, for Optionals it returns as real Optional. Fixes mockito#2865
AndreasTu · Aug 17, 2023 · 3118cc4 · 3118cc4
1 parent cb75cec
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diff --git a/src/main/java/org/mockito/internal/stubbing/defaultanswers/ReturnsDeepStubs.java b/src/main/java/org/mockito/internal/stubbing/defaultanswers/ReturnsDeepStubs.java
@@ -9,6 +9,11 @@
 
 import java.io.IOException;
 import java.io.Serializable;
+import java.lang.reflect.Method;
+import java.util.Optional;
+import java.util.OptionalDouble;
+import java.util.OptionalInt;
+import java.util.OptionalLong;
 
 import org.mockito.MockSettings;
 import org.mockito.Mockito;
@@ -48,6 +53,10 @@ public class ReturnsDeepStubs implements Answer<Object>, Serializable {
 
     @Override
     public Object answer(InvocationOnMock invocation) throws Throwable {
+        Object answer = handleDefaultAnswersForWellKnownTypes(invocation);
+        if (answer != null) {
+            return answer;
+        }
         GenericMetadataSupport returnTypeGenericMetadata =
                 actualParameterizedType(invocation.getMock())
                         .resolveGenericReturnType(invocation.getMethod());
@@ -76,6 +85,34 @@ public Object answer(InvocationOnMock invocation) throws Throwable {
         return deepStub(invocation, returnTypeGenericMetadata);
     }
 
+    /**
+     * This returns default answers for well known methods of the following special types:
+     * <ul>
+     *     <li>{@link Optional}</li>
+     *     <li>{@link OptionalLong}</li>
+     *     <li>{@link OptionalDouble}</li>
+     *     <li>{@link OptionalInt}</li>
+     * </ul>
+     *
+     * <p>Issue #2865: Default mock of Optional is not empty when using RETURN_DEEP_STUBS
+     *
+     * @param invocation the invocation
+     * @return the answer or {@code null}, if no default answer was found.
+     */
+    private Object handleDefaultAnswersForWellKnownTypes(InvocationOnMock invocation) {
+        Method method = invocation.getMethod();
+        Class<?> declaringClass = method.getDeclaringClass();
+        if (declaringClass == Optional.class
+                || declaringClass == OptionalLong.class
+                || declaringClass == OptionalDouble.class
+                || declaringClass == OptionalInt.class) {
+            if (method.getName().equals("isEmpty") && method.getParameterCount() == 0) {
+                return true;
+            }
+        }
+        return null;
+    }
+
     private Object deepStub(
             InvocationOnMock invocation, GenericMetadataSupport returnTypeGenericMetadata)
             throws Throwable {

diff --git a/src/test/java/org/mockito/internal/stubbing/defaultanswers/ReturnsOptionalMocksTest.java b/src/test/java/org/mockito/internal/stubbing/defaultanswers/ReturnsOptionalMocksTest.java
@@ -0,0 +1,171 @@
+/*
+ * Copyright (c) 2023 Mockito contributors
+ * This program is made available under the terms of the MIT License.
+ */
+package org.mockito.internal.stubbing.defaultanswers;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.Mockito.RETURNS_DEEP_STUBS;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.mockingDetails;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+import java.util.Optional;
+import java.util.OptionalDouble;
+import java.util.OptionalInt;
+import java.util.OptionalLong;
+
+import org.junit.Test;
+
+public class ReturnsOptionalMocksTest {
+    private interface Type {
+        Optional<String> getOptString();
+
+        OptionalLong getOptLong();
+
+        OptionalDouble getOptDouble();
+
+        OptionalInt getOptInt();
+    }
+
+    @Test
+    public void deepStubs_Optional_should_return_mocked_optional_Issue2865() {
+        final Type type = mock(Type.class, RETURNS_DEEP_STUBS);
+        assertThat(type.getOptString()).isNotEqualTo(Optional.empty());
+        assertIsMock(type.getOptString());
+    }
+
+    @Test
+    public void deepStubs_OptionalLong_should_return_mocked_optional_Issue2865() {
+        final Type type = mock(Type.class, RETURNS_DEEP_STUBS);
+        assertThat(type.getOptLong()).isNotEqualTo(OptionalLong.empty());
+        assertIsMock(type.getOptLong());
+    }
+
+    @Test
+    public void deepStubs_OptionalDouble_should_return_mocked_optional_Issue2865() {
+        final Type type = mock(Type.class, RETURNS_DEEP_STUBS);
+        assertThat(type.getOptDouble()).isNotEqualTo(OptionalDouble.empty());
+        assertIsMock(type.getOptDouble());
+    }
+
+    @Test
+    public void deepStubs_OptionalInt_should_return_mocked_optional() {
+        final Type type = mock(Type.class, RETURNS_DEEP_STUBS);
+        assertThat(type.getOptInt()).isNotEqualTo(OptionalInt.empty());
+        assertIsMock(type.getOptInt());
+    }
+
+    @Test
+    public void normal_mock_Optional_should_return_normal_optional_empty() {
+        final Type type = mock(Type.class);
+        assertThat(type.getOptString()).isEqualTo(Optional.empty());
+        assertIsNoMock(type.getOptString());
+    }
+
+    @Test
+    public void normal_mock_OptionalLong_should_return_normal_optional_empty() {
+        final Type type = mock(Type.class);
+        assertThat(type.getOptLong()).isEqualTo(OptionalLong.empty());
+    }
+
+    @Test
+    public void normal_mock_OptionalDouble_should_return_normal_optional_empty() {
+        final Type type = mock(Type.class);
+        assertThat(type.getOptDouble()).isEqualTo(OptionalDouble.empty());
+    }
+
+    @Test
+    public void normal_mock_OptionalInt_should_return_normal_optional_empty() {
+        final Type type = mock(Type.class);
+        assertThat(type.getOptInt()).isEqualTo(OptionalInt.empty());
+    }
+
+    @Test
+    public void deepStubs_Optional_isPresent_isEmpty_Issue2865() {
+        final Type type = mock(Type.class, RETURNS_DEEP_STUBS);
+        Optional<String> opt = type.getOptString();
+        assertThat(opt.isPresent()).isEqualTo(false);
+        assertThat(opt.isEmpty()).isEqualTo(true);
+    }
+
+    @Test
+    public void deepStubs_Optional_isEmpty_is_mockable() {
+        final Type type = mock(Type.class, RETURNS_DEEP_STUBS);
+        Optional<String> opt = type.getOptString();
+        assertThat(opt.isEmpty()).isEqualTo(true);
+        when(opt.isEmpty()).thenReturn(false);
+        assertThat(opt.isEmpty()).isEqualTo(false);
+        verify(opt, times(2)).isEmpty();
+    }
+
+    @Test
+    public void deepStubs_OptionalLong_isPresent_isEmpty_Issue2865() {
+        final Type type = mock(Type.class, RETURNS_DEEP_STUBS);
+        OptionalLong opt = type.getOptLong();
+        assertThat(opt.isPresent()).isEqualTo(false);
+        assertThat(opt.isEmpty()).isEqualTo(true);
+    }
+
+    @Test
+    public void deepStubs_OptionalDouble_isPresent_isEmpty_Issue2865() {
+        final Type type = mock(Type.class, RETURNS_DEEP_STUBS);
+        OptionalDouble opt = type.getOptDouble();
+        assertThat(opt.isPresent()).isEqualTo(false);
+        assertThat(opt.isEmpty()).isEqualTo(true);
+    }
+
+    @Test
+    public void deepStubs_OptionalInt_isPresent_isEmpty_Issue2865() {
+        final Type type = mock(Type.class, RETURNS_DEEP_STUBS);
+        OptionalInt opt = type.getOptInt();
+        assertThat(opt.isPresent()).isEqualTo(false);
+        assertThat(opt.isEmpty()).isEqualTo(true);
+    }
+
+    @Test
+    public void normal_mock_Optional_isPresent_isEmpty_Issue2865() {
+        final Type type = mock(Type.class);
+
+        Optional<String> opt = type.getOptString();
+        assertThat(opt.isPresent()).isEqualTo(false);
+        assertThat(opt.isEmpty()).isEqualTo(true);
+    }
+
+    @Test
+    public void normal_mock_OptionalLong_isPresent_isEmpty_Issue2865() {
+        final Type type = mock(Type.class);
+
+        OptionalLong opt = type.getOptLong();
+        assertThat(opt.isPresent()).isEqualTo(false);
+        assertThat(opt.isEmpty()).isEqualTo(true);
+    }
+
+    @Test
+    public void normal_mock_OptionalDouble_isPresent_isEmpty_Issue2865() {
+        final Type type = mock(Type.class);
+
+        OptionalDouble opt = type.getOptDouble();
+        assertThat(opt.isPresent()).isEqualTo(false);
+        assertThat(opt.isEmpty()).isEqualTo(true);
+    }
+
+    @Test
+    public void normal_mock_OptionalInt_isPresent_isEmpty_Issue2865() {
+        final Type type = mock(Type.class);
+
+        OptionalInt opt = type.getOptInt();
+        assertThat(opt.isPresent()).isEqualTo(false);
+        assertThat(opt.isEmpty()).isEqualTo(true);
+    }
+
+    private void assertIsMock(Object mock) {
+        assertThat(mockingDetails(mock).isMock()).isTrue();
+    }
+
+    private void assertIsNoMock(Object mock) {
+        assertThat(mockingDetails(mock).isMock()).isFalse();
+    }
+}