add check test

test/unit/checks_test.dart

@@ -0,0 +1,30 @@
+import 'dart:convert';
+
+import 'package:github/src/common/model/checks.dart';
+import 'package:test/test.dart';
+
+void main() {
+  group('Check run', () {
+    test('CheckRun fromJson', () {
+      // This is a truncated version of the response
+      const checkRunJson = '''{
+        "id": 4,
+        "head_sha": "ce587453ced02b1526dfb4cb910479d431683101",
+        "external_id": "",
+        "details_url": "https://example.com",
+        "status": "completed",
+        "conclusion": "neutral",
+        "started_at": "2018-05-04T01:14:52Z",
+        "name": "mighty_readme",
+        "check_suite": {
+          "id": 5
+        }
+      }''';
+      final checkRun = CheckRun.fromJson(jsonDecode(checkRunJson));
+
+      expect(checkRun.id, 4);
+      expect(checkRun.name, 'mighty_readme');
+      expect(checkRun.conclusion, CheckRunConclusion.neutral);
+    });
+  });
+}