diff --git a/test/mk_coordinate_region_test.dart b/test/mk_coordinate_region_test.dart
index 1c8172f..d6bcc17 100644
--- a/test/mk_coordinate_region_test.dart
+++ b/test/mk_coordinate_region_test.dart
@@ -3,21 +3,6 @@ import 'package:flutter_test/flutter_test.dart';
 import 'package:mapkit_flutter/mapkit_flutter.dart';
 
 void main() {
-  group('MKCoordinateSpan', () {
-    test('equality is value-based', () {
-      const a = MKCoordinateSpan(latitudeDelta: 1, longitudeDelta: 2);
-      const b = MKCoordinateSpan(latitudeDelta: 1, longitudeDelta: 2);
-      check(a).equals(b);
-      check(a.hashCode).equals(b.hashCode);
-    });
-
-    test('rejects negative deltas', () {
-      check(
-        () => MKCoordinateSpan(latitudeDelta: -1, longitudeDelta: 0),
-      ).throws<AssertionError>();
-    });
-  });
-
   group('MKCoordinateRegion.containing', () {
     test('returns null for no coordinates', () {
       check(MKCoordinateRegion.containing(const [])).isNull();
diff --git a/test/mk_coordinate_span_test.dart b/test/mk_coordinate_span_test.dart
new file mode 100644
index 0000000..66a1484
--- /dev/null
+++ b/test/mk_coordinate_span_test.dart
@@ -0,0 +1,39 @@
+import 'package:checks/checks.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:mapkit_flutter/mapkit_flutter.dart';
+
+void main() {
+  group('MKCoordinateSpan', () {
+    test('equality is value-based', () {
+      const a = MKCoordinateSpan(latitudeDelta: 1, longitudeDelta: 2);
+      const b = MKCoordinateSpan(latitudeDelta: 1, longitudeDelta: 2);
+      check(a).equals(b);
+      check(a.hashCode).equals(b.hashCode);
+    });
+
+    test('rejects negative deltas', () {
+      check(
+        () => MKCoordinateSpan(latitudeDelta: -1, longitudeDelta: 0),
+      ).throws<AssertionError>();
+      check(
+        () => MKCoordinateSpan(latitudeDelta: 0, longitudeDelta: -1),
+      ).throws<AssertionError>();
+    });
+
+    test('round-trips through the platform type', () {
+      const original = MKCoordinateSpan(
+        latitudeDelta: 1.5,
+        longitudeDelta: 2.5,
+      );
+      final platform = original.toPlatform();
+      check(platform.latitudeDelta).equals(1.5);
+      check(platform.longitudeDelta).equals(2.5);
+      check(MKCoordinateSpan.fromPlatform(platform)).equals(original);
+    });
+
+    test('toString representation', () {
+      const span = MKCoordinateSpan(latitudeDelta: 1.2, longitudeDelta: 3.4);
+      check(span.toString()).equals('MKCoordinateSpan(1.2, 3.4)');
+    });
+  });
+}