contexts test, fix bug, missing field in device

lib/src/base.dart

@@ -789,12 +789,14 @@ class Device {
 
     if (storageSize != null) json['storage_size'] = storageSize;
 
+    if (freeStorage != null) json['free_storage'] = freeStorage;
+
     if (externalStorageSize != null) {
       json['external_storage_size'] = externalStorageSize;
     }
 
     if (externalFreeStorage != null) {
-      json['exterenal_free_storage'] = externalFreeStorage;
+      json['external_free_storage'] = externalFreeStorage;
     }
 
     if (bootTime != null) json['boot_time'] = bootTime.toIso8601String();

test/contexts_test.dart

@@ -0,0 +1,95 @@
+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'package:sentry/sentry.dart';
+import 'package:test/test.dart';
+
+void main() {
+  group(Contexts, () {
+    test('serializes to JSON', () {
+      final testDevice = Device(
+        name: 'testDevice',
+        family: 'testFamily',
+        model: 'testModel',
+        modelId: 'testModelId',
+        arch: 'testArch',
+        batteryLevel: 23,
+        orientation: Orientation.landscape,
+        manufacturer: 'testOEM',
+        brand: 'testBrand',
+        screenResolution: '123x345',
+        screenDensity: '99',
+        screenDpi: '100',
+        online: false,
+        charging: true,
+        lowMemory: false,
+        simulator: true,
+        memorySize: 1234567,
+        freeMemory: 12345,
+        usableMemory: 9876,
+        storageSize: 1234567,
+        freeStorage: 1234567,
+        externalStorageSize: 98765,
+        externalFreeStorage: 98765,
+        bootTime: DateTime.fromMicrosecondsSinceEpoch(0),
+        timezone: 'Australia/Melbourne',
+      );
+      final testOS = OperatingSystem(name: 'testOS');
+      final testRuntimes = [
+        Runtime(name: 'testRT1', version: '1.0'),
+        Runtime(name: 'testRT2', version: '2.3.1'),
+      ];
+      final testApp = App(version: '1.2.3');
+      final testBrowser = Browser(version: '12.3.4');
+
+      final contexts = Contexts(
+        device: testDevice,
+        operatingSystem: testOS,
+        runtimes: testRuntimes,
+        app: testApp,
+        browser: testBrowser,
+      );
+
+      expect(
+        contexts.toJson(),
+        <String, dynamic>{
+          'device': {
+            'name': 'testDevice',
+            'family': 'testFamily',
+            'model': 'testModel',
+            'model_id': 'testModelId',
+            'arch': 'testArch',
+            'battery_level': 23,
+            'orientation': 'landscape',
+            'manufacturer': 'testOEM',
+            'brand': 'testBrand',
+            'screen_resolution': '123x345',
+            'screen_density': '99',
+            'screen_dpi': '100',
+            'online': false,
+            'charging': true,
+            'low_memory': false,
+            'simulator': true,
+            'memory_size': 1234567,
+            'free_memory': 12345,
+            'usable_memory': 9876,
+            'storage_size': 1234567,
+            'free_storage': 1234567,
+            'external_storage_size': 98765,
+            'external_free_storage': 98765,
+            'boot_time': '1970-01-01T10:00:00.000',
+            'timezone': 'Australia/Melbourne',
+          },
+          'os': {
+            'name': 'testOS',
+          },
+          'testrt1': {'name': 'testRT1', 'type': 'runtime', 'version': '1.0'},
+          'testrt2': {'name': 'testRT2', 'type': 'runtime', 'version': '2.3.1'},
+          'app': {'app_version': '1.2.3'},
+          'browser': {'version': '12.3.4'},
+        },
+      );
+    });
+  });
+}