Add HaveCount assertion to JToken

Author: Ronald Kroon

Src/FluentAssertions.Json.Shared/JTokenAssertions.cs

@@ -313,5 +313,28 @@ public AndWhichConstraint<JTokenAssertions, JToken> ContainSingleItem(string bec
                 return new AndWhichConstraint<JTokenAssertions, JToken>(this, constraint.Which);
             }
         }
+
+        /// <summary>
+        /// Asserts that the number of items in the current <see cref="JToken" /> matches the supplied <paramref name="expected" /> amount.
+        /// </summary>
+        /// <param name="expected">The expected number of items in the current <see cref="JToken" />.</param>
+        /// <param name="because">
+        /// A formatted phrase as is supported by <see cref="string.Format(string,object[])" /> explaining why the assertion
+        /// is needed. If the phrase does not start with the word <i>because</i>, it is prepended automatically.
+        /// </param>
+        /// <param name="becauseArgs">
+        /// Zero or more objects to format using the placeholders in <see cref="because" />.
+        /// </param>
+        public AndConstraint<JTokenAssertions> HaveCount(int expected, string because = "", params object[] becauseArgs)
+        {
+            var formatter = new JTokenFormatter();
+            string formattedDocument = formatter.ToString(Subject).Replace("{", "{{").Replace("}", "}}");
+
+            using (new AssertionScope("JSON document " + formattedDocument))
+            {
+                EnumerableSubject.HaveCount(expected, because, becauseArgs);
+                return new AndConstraint<JTokenAssertions>(this);
+            }
+        }
     }
 }

Tests/FluentAssertions.Json.Shared.Specs/JTokenAssertionsSpecs.cs

@@ -552,5 +552,126 @@ public void When_jtoken_is_an_array_with_multiple_items_ContainSingleItem_should
         }
 
         #endregion ContainSingleItem
+
+        #region HaveCount
+
+        [TestMethod]
+        public void When_expecting_the_actual_number_of_elements_HaveCount_should_succeed()
+        {
+            //-----------------------------------------------------------------------------------------------------------
+            // Arrange
+            //-----------------------------------------------------------------------------------------------------------
+            var subject = JToken.Parse("{ id: 42, admin: true }");
+
+            //-----------------------------------------------------------------------------------------------------------
+            // Act
+            //-----------------------------------------------------------------------------------------------------------
+            Action act = () => subject.Should().HaveCount(2);
+
+            //-----------------------------------------------------------------------------------------------------------
+            // Assert
+            //-----------------------------------------------------------------------------------------------------------
+            act.ShouldNotThrow();
+        }
+
+        [TestMethod]
+        public void When_expecting_the_actual_number_of_elements_HaveCount_should_enable_consecutive_assertions()
+        {
+            //-----------------------------------------------------------------------------------------------------------
+            // Arrange
+            //-----------------------------------------------------------------------------------------------------------
+            var subject = JToken.Parse("{ id: 42 }");
+
+            //-----------------------------------------------------------------------------------------------------------
+            // Act
+            //-----------------------------------------------------------------------------------------------------------
+            JTokenAssertions and = subject.Should().HaveCount(1).And;
+
+            //-----------------------------------------------------------------------------------------------------------
+            // Assert
+            //-----------------------------------------------------------------------------------------------------------
+            and.Be(subject);
+        }
+
+        [TestMethod]
+        public void When_jtoken_is_null_HaveCount_should_fail()
+        {
+            //-----------------------------------------------------------------------------------------------------------
+            // Arrange
+            //-----------------------------------------------------------------------------------------------------------
+            JToken subject = null;
+
+            //-----------------------------------------------------------------------------------------------------------
+            // Act
+            //-----------------------------------------------------------------------------------------------------------
+            Action act = () => subject.Should().HaveCount(1, "null is not allowed");
+
+            //-----------------------------------------------------------------------------------------------------------
+            // Assert
+            //-----------------------------------------------------------------------------------------------------------
+            act.ShouldThrow<AssertFailedException>()
+                .WithMessage($"Expected JSON document <null> to contain 1 item(s) because null is not allowed, but found <null>.");
+        }
+
+        [TestMethod]
+        public void When_expecting_a_different_number_of_elements_than_the_actual_number_HaveCount_should_fail()
+        {
+            //-----------------------------------------------------------------------------------------------------------
+            // Arrange
+            //-----------------------------------------------------------------------------------------------------------
+            var subject = JToken.Parse("{ }");
+
+            //-----------------------------------------------------------------------------------------------------------
+            // Act
+            //-----------------------------------------------------------------------------------------------------------
+            Action act = () => subject.Should().HaveCount(1, "numbers matter");
+
+            //-----------------------------------------------------------------------------------------------------------
+            // Assert
+            //-----------------------------------------------------------------------------------------------------------
+            act.ShouldThrow<AssertFailedException>()
+                .WithMessage($"Expected JSON document * to contain 1 item(s) because numbers matter, but found 0.");
+        }
+
+        [TestMethod]
+        public void When_expecting_the_actual_number_of_array_items_HaveCount_should_succeed()
+        {
+            //-----------------------------------------------------------------------------------------------------------
+            // Arrange
+            //-----------------------------------------------------------------------------------------------------------
+            var subject = JToken.Parse("[ 'Hello', 'World!' ]");
+
+            //-----------------------------------------------------------------------------------------------------------
+            // Act
+            //-----------------------------------------------------------------------------------------------------------
+            Action act = () => subject.Should().HaveCount(2);
+
+            //-----------------------------------------------------------------------------------------------------------
+            // Assert
+            //-----------------------------------------------------------------------------------------------------------
+            act.ShouldNotThrow();
+        }
+
+        [TestMethod]
+        public void When_expecting_a_different_number_of_array_items_than_the_actual_number_HaveCount_should_fail()
+        {
+            //-----------------------------------------------------------------------------------------------------------
+            // Arrange
+            //-----------------------------------------------------------------------------------------------------------
+            var subject = JToken.Parse("[ 'Hello', 'World!' ]");
+
+            //-----------------------------------------------------------------------------------------------------------
+            // Act
+            //-----------------------------------------------------------------------------------------------------------
+            Action act = () => subject.Should().HaveCount(3, "the more the better");
+
+            //-----------------------------------------------------------------------------------------------------------
+            // Assert
+            //-----------------------------------------------------------------------------------------------------------
+            act.ShouldThrow<AssertFailedException>()
+                .WithMessage($"Expected JSON document * to contain 3 item(s) because the more the better, but found 2.");
+        }
+
+        #endregion HaveCount
     }
 }