CSHARP-2344: Update ChangeStream tests for 4.1.1 "drop" notifications.

Author: DmitryLukyanov

src/MongoDB.Driver.Core/ChangeStreamOperationType.cs

@@ -43,6 +43,10 @@ public enum ChangeStreamOperationType
         /// <summary>
         /// A rename operation type.
         /// </summary>
-        Rename
+        Rename,
+        /// <summary>
+        /// A drop operation type.
+        /// </summary>
+        Drop
     }
 }

src/MongoDB.Driver.Core/ChangeStreamOperationTypeSerializer.cs

@@ -52,6 +52,7 @@ public override ChangeStreamOperationType Deserialize(BsonDeserializationContext
                 case "replace": return ChangeStreamOperationType.Replace;
                 case "update": return ChangeStreamOperationType.Update;
                 case "rename": return ChangeStreamOperationType.Rename;
+                case "drop": return ChangeStreamOperationType.Drop;
                 default: throw new FormatException($"Invalid ChangeStreamOperationType: \"{stringValue}\".");
             }
         }
@@ -69,6 +70,7 @@ public override void Serialize(BsonSerializationContext context, BsonSerializati
                 case ChangeStreamOperationType.Replace: writer.WriteString("replace"); break;
                 case ChangeStreamOperationType.Update: writer.WriteString("update"); break;
                 case ChangeStreamOperationType.Rename: writer.WriteString("rename"); break;
+                case ChangeStreamOperationType.Drop: writer.WriteString("drop"); break;
                 default: throw new ArgumentException($"Invalid ChangeStreamOperationType: {value}.", nameof(value));
             }
         }

tests/MongoDB.Driver.Core.Tests/ChangeStreamDocumentTests.cs

@@ -177,6 +177,7 @@ public void FullDocument_should_return_null_when_not_present()
         [InlineData("replace", ChangeStreamOperationType.Replace)]
         [InlineData("delete", ChangeStreamOperationType.Delete)]
         [InlineData("rename", ChangeStreamOperationType.Rename)]
+        [InlineData("drop", ChangeStreamOperationType.Drop)]
         public void OperationType_should_return_expected_result(string operationTypeName, ChangeStreamOperationType expectedResult)
         {
             var backingDocument = new BsonDocument { { "other", 1 }, { "operationType", operationTypeName } };

tests/MongoDB.Driver.Core.Tests/ChangeStreamOperationTypeSerializerTests.cs

@@ -31,6 +31,7 @@ public class ChangeStreamOperationTypeSerializerTests
         [InlineData("\"replace\"", ChangeStreamOperationType.Replace)]
         [InlineData("\"update\"", ChangeStreamOperationType.Update)]
         [InlineData("\"rename\"", ChangeStreamOperationType.Rename)]
+        [InlineData("\"drop\"", ChangeStreamOperationType.Drop)]
         public void Deserialize_should_return_expected_result(string json, ChangeStreamOperationType expectedResult)
         {
             var subject = CreateSubject();
@@ -69,6 +70,7 @@ public void Deserialize_should_throw_when_input_is_invalid()
         [InlineData(ChangeStreamOperationType.Replace, "\"replace\"")]
         [InlineData(ChangeStreamOperationType.Update, "\"update\"")]
         [InlineData(ChangeStreamOperationType.Rename, "\"rename\"")]
+        [InlineData(ChangeStreamOperationType.Drop, "\"drop\"")]
         public void Serialize_should_have_expected_result(ChangeStreamOperationType value, string expectedResult)
         {
             var subject = CreateSubject();
@@ -87,7 +89,7 @@ public void Serialize_should_have_expected_result(ChangeStreamOperationType valu
 
         [Theory]
         [InlineData(-1)]
-        [InlineData(6)]
+        [InlineData(7)]
         public void Serialize_should_throw_when_value_is_invalid(int valueAsInt)
         {
             var subject = CreateSubject();