added tests for null arguments to AsReadOnly extensions

dotnet · Nov 22, 2021 · 090374e · 090374e
1 parent a72b3f9
commit 090374e
Showing 1 changed file with 14 additions and 0 deletions.
diff --git a/src/libraries/System.Collections/tests/Generic/CollectionExtensionsTests.cs b/src/libraries/System.Collections/tests/Generic/CollectionExtensionsTests.cs
@@ -125,5 +125,19 @@ public void AsReadOnly_TurnsIDictionaryIntoReadOnlyDictionary()
             Assert.Equal(dictionary["key2"], readOnlyDictionary["key2"]);
             Assert.Equal(dictionary.Count, readOnlyDictionary.Count);
         }
+
+        [Fact]
+        public void AsReadOnly_NullIList_ThrowsArgumentNullException()
+        {
+            IList<string> list = null;
+            Assert.Throws<ArgumentNullException>(() => list.AsReadOnly());
+        }
+
+        [Fact]
+        public void AsReadOnly_NullIDictionary_ThrowsArgumentNullException()
+        {
+            IDictionary<string, string> dictionary = null;
+            Assert.Throws<ArgumentNullException>(() => dictionary.AsReadOnly());
+        }
     }
 }