reuse JToken.Parse error handling

Author: sam.segers

Src/FluentAssertions.Json/JTokenAssertions.cs

@@ -54,19 +54,7 @@ public JTokenAssertions(JToken subject, AssertionChain assertionChain)
     public AndConstraint<JTokenAssertions> BeEquivalentTo(string expected, string because = "",
         params object[] becauseArgs)
     {
-        JToken parsedExpected;
-        try
-        {
-            parsedExpected = JToken.Parse(expected);
-        }
-        catch (Exception ex)
-        {
-            throw new ArgumentException(
-                $"Unable to parse expected JSON string:{Environment.NewLine}" +
-                $"{expected}{Environment.NewLine}" +
-                "Check inner exception for more details.",
-                nameof(expected), ex);
-        }
+        JToken parsedExpected = Parse(expected, nameof(expected));
 
         return BeEquivalentTo(parsedExpected, because, becauseArgs);
     }
@@ -150,19 +138,7 @@ private AndConstraint<JTokenAssertions> BeEquivalentTo(JToken expected, bool ign
     public AndConstraint<JTokenAssertions> NotBeEquivalentTo(string unexpected, string because = "",
         params object[] becauseArgs)
     {
-        JToken parsedUnexpected;
-        try
-        {
-            parsedUnexpected = JToken.Parse(unexpected);
-        }
-        catch (Exception ex)
-        {
-            throw new ArgumentException(
-                $"Unable to parse unexpected JSON string:{Environment.NewLine}" +
-                $"{unexpected}{Environment.NewLine}" +
-                "Check inner exception for more details.",
-                nameof(unexpected), ex);
-        }
+        JToken parsedUnexpected = Parse(unexpected, nameof(unexpected));
 
         return NotBeEquivalentTo(parsedUnexpected, because, becauseArgs);
     }
@@ -448,19 +424,7 @@ public AndConstraint<JTokenAssertions> HaveCount(int expected, string because =
     /// </code>
     public AndConstraint<JTokenAssertions> ContainSubtree(string subtree, string because = "", params object[] becauseArgs)
     {
-        JToken subtreeToken;
-        try
-        {
-            subtreeToken = JToken.Parse(subtree);
-        }
-        catch (Exception ex)
-        {
-            throw new ArgumentException(
-                $"Unable to parse expected JSON string:{Environment.NewLine}" +
-                $"{subtree}{Environment.NewLine}" +
-                "Check inner exception for more details.",
-                nameof(subtree), ex);
-        }
+        JToken subtreeToken = Parse(subtree, nameof(subtree));
 
         return ContainSubtree(subtreeToken, because, becauseArgs);
     }
@@ -496,6 +460,22 @@ public AndConstraint<JTokenAssertions> ContainSubtree(JToken subtree, string bec
         return BeEquivalentTo(subtree, true, options => options, because, becauseArgs);
     }
 
+    private static JToken Parse(string json, string paramName)
+    {
+        try
+        {
+            return JToken.Parse(json);
+        }
+        catch (Exception ex)
+        {
+            throw new ArgumentException(
+                $"Unable to parse {paramName} JSON string:{Environment.NewLine}" +
+                $"{json}{Environment.NewLine}" +
+                "Check inner exception for more details.",
+                paramName, ex);
+        }
+    }
+
 #pragma warning disable CA1822 // Making this method static is a breaking chan
     public string Format(JToken value, bool useLineBreaks = false)
     {

Tests/FluentAssertions.Json.Specs/JTokenAssertionsSpecs.cs

@@ -943,7 +943,7 @@ public void When_checking_subtree_with_an_invalid_expected_string_it_should_prov
         // Act & Assert
         actualJson.Should().Invoking(x => x.ContainSubtree(invalidSubtree))
             .Should().Throw<ArgumentException>()
-            .WithMessage($"Unable to parse expected JSON string:{invalidSubtree}*")
+            .WithMessage($"Unable to parse subtree JSON string:{invalidSubtree}*")
             .WithInnerException<JsonReaderException>();
     }