Implement diff-reporter PoC (#5)

tests/Recordingtest.DiffReporter.Tests/DifferTests.cs

@@ -0,0 +1,98 @@
+using System.Text.Json;
+using Recordingtest.DiffReporter;
+using Xunit;
+
+namespace Recordingtest.DiffReporter.Tests;
+
+public class DifferTests
+{
+    private static string TempDir()
+    {
+        var d = Path.Combine(Path.GetTempPath(), "diffrep-" + Guid.NewGuid().ToString("N"));
+        Directory.CreateDirectory(d);
+        return d;
+    }
+
+    [Fact]
+    public void Identical_JsonFiles_ReturnsIdentical()
+    {
+        var dir = TempDir();
+        var a = Path.Combine(dir, "a.json");
+        var b = Path.Combine(dir, "b.json");
+        File.WriteAllText(a, "{\"x\":1,\"y\":\"hi\"}");
+        File.WriteAllText(b, "{\"x\":1,\"y\":\"hi\"}");
+        var r = Differ.Compare(a, b);
+        Assert.True(r.Identical);
+        Assert.Empty(r.Hunks);
+    }
+
+    [Fact]
+    public void OneFieldChanged_JsonFiles_OneHunk()
+    {
+        var dir = TempDir();
+        var a = Path.Combine(dir, "a.json");
+        var b = Path.Combine(dir, "b.json");
+        File.WriteAllText(a, "{\"x\":1,\"y\":\"hi\"}");
+        File.WriteAllText(b, "{\"x\":2,\"y\":\"hi\"}");
+        var r = Differ.Compare(a, b);
+        Assert.False(r.Identical);
+        Assert.Single(r.Hunks);
+        Assert.Equal("changed", r.Hunks[0].Kind);
+    }
+
+    [Fact]
+    public void BinaryDiff_ReturnsHexSummary()
+    {
+        var dir = TempDir();
+        var a = Path.Combine(dir, "a.bin");
+        var b = Path.Combine(dir, "b.bin");
+        File.WriteAllBytes(a, new byte[] { 0x00, 0x01, 0x02, 0xFF, 0x80 });
+        File.WriteAllBytes(b, new byte[] { 0x00, 0x01, 0x03, 0xFE, 0x80 });
+        var r = Differ.Compare(a, b);
+        Assert.False(r.Identical);
+        Assert.NotEmpty(r.Hunks);
+        foreach (var h in r.Hunks)
+        {
+            // hex strings only
+            Assert.Matches("^[0-9A-F]*$", h.Before);
+            Assert.Matches("^[0-9A-F]*$", h.After);
+        }
+    }
+
+    [Fact]
+    public void Cli_IdenticalFiles_ExitZero_And_DiffJsonExists()
+    {
+        var dir = TempDir();
+        var a = Path.Combine(dir, "a.json");
+        var b = Path.Combine(dir, "b.json");
+        File.WriteAllText(a, "{\"x\":1}");
+        File.WriteAllText(b, "{\"x\":1}");
+        var outDir = Path.Combine(dir, "out");
+        var code = Cli.Program.Main(new[] { "--approved", a, "--received", b, "--out", outDir });
+        Assert.Equal(0, code);
+        Assert.True(File.Exists(Path.Combine(outDir, "diff.json")));
+        Assert.True(File.Exists(Path.Combine(outDir, "diff.md")));
+    }
+
+    [Fact]
+    public void TriageReadable_DiffJson_CanBeParsed()
+    {
+        var dir = TempDir();
+        var a = Path.Combine(dir, "a.json");
+        var b = Path.Combine(dir, "b.json");
+        File.WriteAllText(a, "{\"x\":1}");
+        File.WriteAllText(b, "{\"x\":2}");
+        var outDir = Path.Combine(dir, "out");
+        var code = Cli.Program.Main(new[] { "--approved", a, "--received", b, "--out", outDir });
+        Assert.Equal(1, code);
+        var json = File.ReadAllText(Path.Combine(outDir, "diff.json"));
+        using var doc = JsonDocument.Parse(json);
+        var root = doc.RootElement;
+        Assert.True(root.TryGetProperty("file", out _));
+        Assert.True(root.TryGetProperty("hunks", out _));
+        Assert.True(root.TryGetProperty("summary", out var summary));
+        Assert.True(summary.TryGetProperty("added", out _));
+        Assert.True(summary.TryGetProperty("removed", out _));
+        Assert.True(summary.TryGetProperty("changed", out _));
+    }
+}