mutate map returns to emptyMap instead of null

hcoles · Oct 27, 2021 · 89b0c2c · 89b0c2c
1 parent afc6fa1
commit 89b0c2c
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diff --git a/README.md b/README.md
@@ -8,6 +8,10 @@ Read all about it at http://pitest.org
 
 ## Releases
 
+### 1.7.3 (unreleased)
+
+* #952 Mutate map return to emptyMap instead of null
+
 ### 1.7.2 
 
 * #943 Change default mutators - replace negate conditional with remove conditional

diff --git a/...va/org/pitest/mutationtest/build/intercept/equivalent/EquivalentReturnMutationFilter.java b/...va/org/pitest/mutationtest/build/intercept/equivalent/EquivalentReturnMutationFilter.java
@@ -268,6 +268,7 @@ public boolean test(MutationDetails a) {
             || returns(method, mutatedInstruction, "java/util/Optional","empty")
             || returns(method, mutatedInstruction, "java/util/stream/Stream","empty")
             || returns(method, mutatedInstruction, "java/util/Collections","emptyList")
+            || returns(method, mutatedInstruction, "java/util/Collections","emptyMap")
             || returns(method, mutatedInstruction, "java/util/Collections","emptySet")
             || returns(method, mutatedInstruction, "java/util/List","of")
             || returns(method, mutatedInstruction, "java/util/Set","of");

diff --git a/...rg/pitest/mutationtest/build/intercept/equivalent/EquivalentReturnMutationFilterTest.java b/...rg/pitest/mutationtest/build/intercept/equivalent/EquivalentReturnMutationFilterTest.java
@@ -11,6 +11,7 @@
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
+import java.util.Map;
 import java.util.Optional;
 import java.util.Set;
 import java.util.stream.Stream;
@@ -143,6 +144,11 @@ public void filtersEquivalentListMutants() {
     this.verifier.assertFiltersNMutationFromClass(1, AlreadyReturnsEmptyList.class);
   }
 
+  @Test
+  public void filtersEquivalentMapMutants() {
+    this.verifier.assertFiltersNMutationFromClass(1, AlreadyReturnsEmptyMap.class);
+  }
+
   @Test
   public void filtersEquivalentListMutantsInTryCatch() {
     this.verifier.assertFiltersNMutationFromClass(1, AlreadyReturnsEmptyListInTryCatch.class);
@@ -317,6 +323,11 @@ public List<Integer> a() {
   }
 }
 
+class AlreadyReturnsEmptyMap {
+  public Map<Integer, Integer> a() {
+    return Collections.emptyMap();
+  }
+}
 
 class AlreadyReturnsEmptyListInTryCatch {
   public List<Integer> a(String s) {

diff --git a/.../org/pitest/mutationtest/engine/gregor/mutators/returns/EmptyObjectReturnValsMutator.java b/.../org/pitest/mutationtest/engine/gregor/mutators/returns/EmptyObjectReturnValsMutator.java
@@ -69,6 +69,7 @@ class AReturnMethodVisitor extends AbstractInsnMutator {
     NON_NULL_MUTATIONS.put("java.util.Optional", returnEmptyOptional());
     NON_NULL_MUTATIONS.put("java.util.stream.Stream", returnEmptyStream());
     NON_NULL_MUTATIONS.put("java.util.List", returnEmptyList());
+    NON_NULL_MUTATIONS.put("java.util.Map", returnEmptyMap());
     NON_NULL_MUTATIONS.put("java.util.Set", returnEmptySet());
     NON_NULL_MUTATIONS.put("java.util.Collection", returnEmptyList());
   }
@@ -204,6 +205,22 @@ public String describe(final int opCode, final MethodInfo methodInfo) {
     };
   }
 
+  private static ZeroOperandMutation returnEmptyMap() {
+    return new ZeroOperandMutation() {
+      @Override
+      public void apply(final int opCode, final MethodVisitor mv) {
+        mv.visitInsn(Opcodes.POP);
+        mv.visitMethodInsn(Opcodes.INVOKESTATIC, "java/util/Collections", "emptyMap", "()Ljava/util/Map;", false);
+        mv.visitInsn(Opcodes.ARETURN);
+      }
+
+      @Override
+      public String describe(final int opCode, final MethodInfo methodInfo) {
+        return "replaced return value with Collections.emptyMap for " + methodInfo.getDescription();
+      }
+    };
+  }
+
   private static ZeroOperandMutation returnEmptySet() {
     return new ZeroOperandMutation() {
       @Override

diff --git a/...c/test/java/org/pitest/mutationtest/engine/gregor/mutators/EmptyObjectReturnValsTest.java b/...c/test/java/org/pitest/mutationtest/engine/gregor/mutators/EmptyObjectReturnValsTest.java
@@ -8,7 +8,9 @@
 
 import java.util.Collection;
 import java.util.Collections;
+import java.util.HashMap;
 import java.util.List;
+import java.util.Map;
 import java.util.Optional;
 import java.util.Set;
 import java.util.concurrent.Callable;
@@ -131,6 +133,12 @@ public void mutatesListToEmptyList() throws Exception {
         createFirstMutant(AList.class), Collections.<String>emptyList());
   }
 
+  @Test
+  public void mutatesMapToEmptyMap() throws Exception {
+    assertMutantCallableReturns(new AMap(),
+            createFirstMutant(AMap.class), Collections.emptyMap());
+  }
+
   @Test
   public void mutatesSetToEmptySet() throws Exception {
     assertMutantCallableReturns(new ASet(),
@@ -235,6 +243,13 @@ public List<String> call() throws Exception {
     }
   }
 
+  private static class AMap implements Callable<Map<String, String>> {
+    @Override
+    public Map<String, String> call() throws Exception {
+      return new HashMap<>();
+    }
+  }
+
   private static class ASet implements Callable<Set<String>> {
     @Override
     public Set<String> call() throws Exception {