Add placeholder escaping in BeEquivalentTo message (#33)

* Added placeholder escaping for `difference` in BeEquivalentTo message creation (#32)

* Add expected message to test

Author: alhimik45

Src/FluentAssertions.Json/JTokenAssertions.cs

@@ -88,13 +88,13 @@ public AndConstraint<JTokenAssertions> BeEquivalentTo(JToken expected, string be
         {
             Difference difference = JTokenDifferentiator.FindFirstDifference(Subject, expected);
 
-            var message = $"JSON document {difference}.{Environment.NewLine}" +
+            var message = $"JSON document {difference?.ToString().Escape(true)}.{Environment.NewLine}" +
                           $"Expected{Environment.NewLine}" +
-                          $"{Format(Subject, true).Replace("{", "{{").Replace("}", "}}")}{Environment.NewLine}" +
+                          $"{Format(Subject, true).Escape(true)}{Environment.NewLine}" +
                           $"to be equivalent to{Environment.NewLine}" +
-                          $"{Format(expected, true).Replace("{", "{{").Replace("}", "}}")}{Environment.NewLine}" +
+                          $"{Format(expected, true).Escape(true)}{Environment.NewLine}" +
                           "{reason}.";
-            
+             
             Execute.Assertion
                 .ForCondition(difference == null)
                 .BecauseOf(because, becauseArgs)

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

@@ -432,7 +432,31 @@ public void When_checking_whether_a_JToken_is_not_equivalent_to_the_string_repre
             action.Should().Throw<XunitException>()
                 .WithMessage("Expected JSON document not to be equivalent*");
         }
-        
+
+        [Fact]
+        public void When_properties_contains_curly_braces_BeEquivalentTo_should_not_fail_with_FormatException()
+        {
+            //-----------------------------------------------------------------------------------------------------------
+            // Arrange
+            //-----------------------------------------------------------------------------------------------------------
+            var actual = JToken.Parse(@"{ ""{a1}"": {b: 1 }}");
+            var expected = JToken.Parse(@"{ ""{a1}"": {b: 2 }}");
+
+            var expectedMessage =
+                "JSON document has a different value at $.{a1}.b." +
+                "Expected" +
+                $"{Format(actual, true)}" +
+                "to be equivalent to" +
+                $"{Format(expected, true)}.";
+
+            //-----------------------------------------------------------------------------------------------------------
+            // Act & Assert
+            //-----------------------------------------------------------------------------------------------------------
+            actual.Should().Invoking(x => x.BeEquivalentTo(expected))
+                .Should().Throw<XunitException>()
+                .WithMessage(expectedMessage);
+        }
+
         #endregion (Not)BeEquivalentTo
 
         #region (Not)HaveValue