Add doesNotReturn to Object assertions (#2453)

Author: scordio

src/main/java/org/assertj/core/api/AbstractObjectAssert.java

@@ -654,7 +654,8 @@ public SELF hasFieldOrProperty(String name) {
    * <p>
    * Private fields are matched by default but this can be changed by calling {@link Assertions#setAllowExtractingPrivateFields(boolean) Assertions.setAllowExtractingPrivateFields(false)}.
    * <p>
-   * If you are looking to chain multiple assertions on different properties in a type safe way, consider chaining {@link #returns(Object, Function)} calls.
+   * If you are looking to chain multiple assertions on different properties in a type safe way, consider chaining
+   * {@link #returns(Object, Function)} and {@link #doesNotReturn(Object, Function)} calls.
    * <p>
    * Example:
    * <pre><code class='java'> public class TolkienCharacter {
@@ -1093,6 +1094,32 @@ public <T> SELF returns(T expected, Function<ACTUAL, T> from) {
     return myself;
   }
 
+  /**
+   * Verifies that the object under test does not return the given expected value from the given {@link Function},
+   * a typical usage is to pass a method reference to assert object's property.
+   * <p>
+   * Wrapping the given {@link Function} with {@link Assertions#from(Function)} makes the assertion more readable.
+   * <p>
+   * Example:
+   * <pre><code class="java"> // from is not mandatory but it makes the assertions more readable
+   * assertThat(frodo).doesNotReturn("Bilbo", from(TolkienCharacter::getName))
+   *                  .doesNotReturn("Bilbo", TolkienCharacter::getName) // no from :(
+   *                  .doesNotReturn(null, from(TolkienCharacter::getRace));</code></pre>
+   *
+   * @param expected the value the object under test method's call should not return.
+   * @param from {@link Function} used to acquire the value to test from the object under test. Must not be {@code null}
+   * @param <T> the expected value type the given {@code method} returns.
+   * @return {@code this} assertion object.
+   * @throws NullPointerException if given {@code from} function is null
+   *
+   * @since 3.22.0
+   */
+  public <T> SELF doesNotReturn(T expected, Function<ACTUAL, T> from) {
+    requireNonNull(from, "The given getter method/Function must not be null");
+    objects.assertNotEqual(info, from.apply(actual), expected);
+    return myself;
+  }
+
   /**
    * Enable using a recursive field by field comparison strategy when calling the chained {@link RecursiveComparisonAssert#isEqualTo(Object) isEqualTo} assertion.
    * <p>

src/main/java/org/assertj/core/api/Assertions.java

@@ -2211,13 +2211,14 @@ public static TemporalUnitOffset byLessThan(long value, TemporalUnit unit) {
   }
 
   /**
-   * A syntax sugar to write fluent assertion using {@link ObjectAssert#returns(Object, Function)}.
+   * A syntax sugar to write fluent assertion using {@link ObjectAssert#returns(Object, Function)} and
+   * {@link ObjectAssert#doesNotReturn(Object, Function)}.
    * <p>
    * Example:
    * <pre><code class="java"> Jedi yoda = new Jedi("Yoda", "Green");
    * assertThat(yoda).returns("Yoda", from(Jedi::getName))
    *                 .returns(2.4, from(Jedi::getHeight))
-   *                 .returns(150, from(Jedi::getWeight)); </code></pre>
+   *                 .doesNotReturn(null, from(Jedi::getWeight)); </code></pre>
    *
    * @param extractor A function to extract test subject's property
    * @param <F> Type of test subject

src/main/java/org/assertj/core/api/BDDAssertions.java

@@ -2601,13 +2601,14 @@ public static TemporalUnitOffset byLessThan(long value, TemporalUnit unit) {
   }
 
   /**
-   * A syntax sugar to write fluent assertion using {@link ObjectAssert#returns(Object, Function)}.
+   * A syntax sugar to write fluent assertion using {@link ObjectAssert#returns(Object, Function)} and
+   * {@link ObjectAssert#doesNotReturn(Object, Function)}.
    * <p>
    * Example:
    * <pre><code class="java"> Jedi yoda = new Jedi("Yoda", "Green");
    * assertThat(yoda).returns("Yoda", from(Jedi::getName))
    *                 .returns(2.4, from(Jedi::getHeight))
-   *                 .returns(150, from(Jedi::getWeight)); </code></pre>
+   *                 .doesNotReturn(null, from(Jedi::getWeight)); </code></pre>
    *
    * @param extractor A function to extract test subject's property
    * @param <F> Type of test subject

src/main/java/org/assertj/core/api/WithAssertions.java

@@ -1772,13 +1772,14 @@ default TemporalUnitOffset byLessThan(long value, TemporalUnit unit) {
   }
 
   /**
-   * A syntax sugar to write fluent assertion using {@link ObjectAssert#returns(Object, Function)}.
+   * A syntax sugar to write fluent assertion using {@link ObjectAssert#returns(Object, Function)} and
+   * {@link ObjectAssert#doesNotReturn(Object, Function)}.
    * <p>
    * Example:
    * <pre><code class="java"> Jedi yoda = new Jedi("Yoda", "Green");
    * assertThat(yoda).returns("Yoda", from(Jedi::getName))
    *                 .returns(2.4, from(Jedi::getHeight))
-   *                 .returns(150, from(Jedi::getWeight)); </code></pre>
+   *                 .doesNotReturn(null, from(Jedi::getWeight)); </code></pre>
    *
    * @param extractor A function to extract test subject's property
    * @param <F> Type of test subject

src/test/java/org/assertj/core/api/object/ObjectAssert_doesNotReturn_Test.java

@@ -0,0 +1,56 @@
+/*
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
+ * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations under the License.
+ *
+ * Copyright 2012-2021 the original author or authors.
+ */
+package org.assertj.core.api.object;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.catchThrowable;
+import static org.assertj.core.api.Assertions.from;
+import static org.assertj.core.api.BDDAssertions.then;
+import static org.mockito.Mockito.verify;
+
+import org.assertj.core.api.ObjectAssert;
+import org.assertj.core.api.ObjectAssertBaseTest;
+import org.assertj.core.test.Jedi;
+import org.junit.jupiter.api.Test;
+
+class ObjectAssert_doesNotReturn_Test extends ObjectAssertBaseTest {
+
+  @Override
+  protected ObjectAssert<Jedi> invoke_api_method() {
+    return assertions.doesNotReturn("Yoda", Jedi::getName);
+  }
+
+  @Override
+  protected void verify_internal_effects() {
+    verify(objects).assertNotEqual(getInfo(assertions), getActual(assertions).getName(), "Yoda");
+  }
+
+  @Test
+  void should_fail_with_throwing_NullPointerException_if_method_is_null() {
+    // WHEN
+    Throwable thrown = catchThrowable(() -> assertions.doesNotReturn("May the force be with you.", null));
+    // THEN
+    then(thrown).isInstanceOf(NullPointerException.class)
+                .hasMessage("The given getter method/Function must not be null");
+  }
+
+  @Test
+  void perform_assertion_like_users() {
+    // GIVEN
+    Jedi yoda = new Jedi("Yoda", "Green");
+    // WHEN/THEN
+    assertThat(yoda).doesNotReturn("Luke", from(Jedi::getName))
+                    .doesNotReturn("Luke", Jedi::getName);
+  }
+
+}

src/test/java/org/assertj/core/api/object/ObjectAssert_returns_Test.java

@@ -13,22 +13,17 @@
 package org.assertj.core.api.object;
 
 import static org.assertj.core.api.Assertions.assertThat;
-import static org.assertj.core.api.Assertions.assertThatThrownBy;
+import static org.assertj.core.api.Assertions.catchThrowable;
 import static org.assertj.core.api.Assertions.from;
+import static org.assertj.core.api.BDDAssertions.then;
 import static org.mockito.Mockito.verify;
 
-import java.util.function.Function;
-
-import org.assertj.core.api.AbstractObjectAssert;
 import org.assertj.core.api.ObjectAssert;
 import org.assertj.core.api.ObjectAssertBaseTest;
-import org.assertj.core.api.ThrowableAssert.ThrowingCallable;
 import org.assertj.core.test.Jedi;
 import org.junit.jupiter.api.Test;
 
 /**
- * Tests for <code>{@link AbstractObjectAssert#returns(Object, Function)}</code>.
- *
  * @author Takuya "Mura-Mi" Murakami
  */
 class ObjectAssert_returns_Test extends ObjectAssertBaseTest {
@@ -45,17 +40,20 @@ protected void verify_internal_effects() {
 
   @Test
   void should_fail_with_throwing_NullPointerException_if_method_is_null() {
-    ThrowingCallable code = () -> assertions.returns("May the force be with you.", null);
-    assertThatThrownBy(code).isExactlyInstanceOf(NullPointerException.class)
-                            .hasMessage("The given getter method/Function must not be null");
+    // WHEN
+    Throwable thrown = catchThrowable(() -> assertions.returns("May the force be with you.", null));
+    // THEN
+    then(thrown).isInstanceOf(NullPointerException.class)
+                .hasMessage("The given getter method/Function must not be null");
   }
 
   @Test
   void perform_assertion_like_users() {
-
+    // GIVEN
     Jedi yoda = new Jedi("Yoda", "Green");
+    // WHEN/THEN
     assertThat(yoda).returns("Yoda", from(Jedi::getName))
                     .returns("Yoda", Jedi::getName);
-
   }
+
 }