test: update fuzzer for writer changes

fuzz/src/fuzz.zig

@@ -16,11 +16,53 @@ fn fuzz(gpa: Allocator, input: []const u8) !void {
     var doc = xml.StaticDocument.init(input);
     var reader = doc.reader(gpa, .{});
     defer reader.deinit();
+
+    var out_bytes = std.ArrayList(u8).init(gpa);
+    defer out_bytes.deinit();
+    const output = xml.streamingOutput(out_bytes.writer());
+    var writer = output.writer(gpa, .{});
+    defer writer.deinit();
+
     while (true) {
         const node = reader.read() catch |err| switch (err) {
             error.MalformedXml => break,
             error.OutOfMemory => return error.OutOfMemory,
         };
-        if (node == .eof) break;
+        switch (node) {
+            .eof => break,
+            .xml_declaration => {
+                try writer.xmlDeclaration(reader.xmlDeclarationEncoding(), reader.xmlDeclarationStandalone());
+            },
+            .comment => {
+                // TODO: not implemented yet
+            },
+            .element_start => {
+                try writer.elementStart(reader.elementName());
+                for (0..reader.attributeCount()) |i| {
+                    try writer.attribute(reader.attributeName(i), try reader.attributeValue(i));
+                }
+            },
+            .element_end => {
+                try writer.elementEnd();
+            },
+            .pi => {
+                try writer.pi(reader.piTarget(), try reader.piData());
+            },
+            .text => {
+                try writer.text(try reader.text());
+            },
+            .cdata => {
+                try writer.text(try reader.cdata());
+            },
+            .character_reference => {
+                var buf: [4]u8 = undefined;
+                const len = std.unicode.utf8Encode(reader.characterReferenceChar(), &buf) catch unreachable;
+                try writer.text(buf[0..len]);
+            },
+            .entity_reference => {
+                const value = xml.predefined_entities.get(reader.entityReferenceName()) orelse unreachable;
+                try writer.text(value);
+            },
+        }
     }
 }