write deserialization tests to ensure we can always deserialize chang…

…es, even after they are modified

backend/FwLite/LcmCrdt.Tests/Changes/ChangeSerializationTests.cs

@@ -1,26 +1,35 @@
 using System.Reflection;
+using System.Runtime.CompilerServices;
 using System.Text.Json;
 using FluentAssertions.Execution;
 using LcmCrdt.Changes;
 using LcmCrdt.Changes.Entries;
 using MiniLcm.Tests.AutoFakerHelpers;
 using SIL.Harmony.Changes;
+using SIL.WritingSystems;
 using Soenneker.Utils.AutoBogus;
 using SystemTextJsonPatch;
 
 namespace LcmCrdt.Tests.Changes;
 
 public class ChangeSerializationTests
 {
+    private static readonly Lazy<JsonSerializerOptions> LazyOptions = new(() =>
+    {
+        var config = new CrdtConfig();
+        LcmCrdtKernel.ConfigureCrdt(config);
+        return config.JsonSerializerOptions;
+    });
+    private static readonly JsonSerializerOptions Options = LazyOptions.Value;
     private static readonly AutoFaker Faker = new()
     {
         Config =
         {
-            Overrides = [new WritingSystemIdOverride()]
+            Overrides = [new WritingSystemIdOverride(), new MultiStringOverride()]
         }
     };
 
-    public static IEnumerable<object[]> Changes()
+    private static IEnumerable<IChange> GeneratedChanges()
     {
         foreach (var type in LcmCrdtKernel.AllChangeTypes())
         {
@@ -34,14 +43,31 @@ public static IEnumerable<object[]> Changes()
             }
             else
             {
-                change = Faker.Generate(type);
+                try
+                {
+                    change = Faker.Generate(type);
+                }
+                catch (Exception e)
+                {
+                    throw new Exception($"Failed to generate change of type {type.Name}", e);
+                }
             }
-            change.Should().NotBeNull($"change type {type.Name} should have been generated");
+
+            change.Should().NotBeNull($"change type {type.Name} should have been generated").And.BeAssignableTo<IChange>();
+            yield return (IChange) change;
+        }
+
+        yield return SetComplexFormComponentChange.NewComplexForm(Guid.NewGuid(), Guid.NewGuid());
+        yield return SetComplexFormComponentChange.NewComponent(Guid.NewGuid(), Guid.NewGuid());
+        yield return SetComplexFormComponentChange.NewComponentSense(Guid.NewGuid(), Guid.NewGuid(), Guid.NewGuid());
+    }
+
+    public static IEnumerable<object[]> Changes()
+    {
+        foreach (var change in GeneratedChanges())
+        {
             yield return [change];
         }
-        yield return [SetComplexFormComponentChange.NewComplexForm(Guid.NewGuid(), Guid.NewGuid())];
-        yield return [SetComplexFormComponentChange.NewComponent(Guid.NewGuid(), Guid.NewGuid())];
-        yield return [SetComplexFormComponentChange.NewComponentSense(Guid.NewGuid(), Guid.NewGuid(), Guid.NewGuid())];
     }
 
     private static readonly MethodInfo PatchMethod = new Func<IChange>(Patch<Entry>).Method.GetGenericMethodDefinition();
@@ -55,13 +81,11 @@ private static IChange Patch<T>() where T : class
     [MemberData(nameof(Changes))]
     public void CanRoundTripChanges(IChange change)
     {
-        var config = new CrdtConfig();
-        LcmCrdtKernel.ConfigureCrdt(config);
         //commit id is not serialized
         change.CommitId = Guid.Empty;
         var type = change.GetType();
-        var json = JsonSerializer.Serialize(change, config.JsonSerializerOptions);
-        var newChange = JsonSerializer.Deserialize(json, type, config.JsonSerializerOptions);
+        var json = JsonSerializer.Serialize(change, Options);
+        var newChange = JsonSerializer.Deserialize(json, type, Options);
         newChange.Should().BeEquivalentTo(change);
     }
 
@@ -79,4 +103,34 @@ public void ChangesIncludesAllValidChangeTypes()
             }
         }
     }
+
+    [Fact]
+    public void CanDeserializeJson()
+    {
+        //this file represents projects which already have changes applied, we want to ensure that we don't break anything.
+        //nothing should ever be removed from this file
+        //if a new property is added then a new json object should be added with that property
+        using var jsonFile = File.OpenRead(GetJsonFilePath("ExistingJson.json"));
+        var changes = JsonSerializer.Deserialize<List<IChange>>(jsonFile, Options);
+        changes.Should().NotBeNullOrEmpty().And.NotContainNulls();
+
+        //ensure that all change types are represented and none should be removed from AllChangeTypes
+        changes.Select(c => c.GetType()).Distinct()
+            .Should().BeEquivalentTo(LcmCrdtKernel.AllChangeTypes());
+    }
+
+    //helper method, can be called manually to regenerate the json file
+    [Fact(Skip = "Only run manually")]
+    public static void GenerateNewJsonFile()
+    {
+        using var jsonFile = File.Open(GetJsonFilePath("NewJson.json"), FileMode.Create);
+        JsonSerializer.Serialize(jsonFile, GeneratedChanges(), Options);
+    }
+
+    private static string GetJsonFilePath(string name, [CallerFilePath] string sourceFile = "")
+    {
+        return Path.Combine(
+            Path.GetDirectoryName(sourceFile) ?? throw new InvalidOperationException("Could not get directory of source file"),
+            name);
+    }
 }