Re-title, format iOS device tests (#10733)

packages/flutter_tools/test/ios/devices_test.dart

@@ -22,7 +22,7 @@ void main() {
   final FakePlatform osx = new FakePlatform.fromPlatform(const LocalPlatform());
   osx.operatingSystem = 'macos';
 
-  group('test screenshot', () {
+  group('screenshot', () {
     MockProcessManager mockProcessManager;
     MockFile mockOutputFile;
     IOSDevice iosDeviceUnderTest;
@@ -32,9 +32,7 @@ void main() {
       mockOutputFile = new MockFile();
     });
 
-    testUsingContext(
-      'screenshot without ideviceinstaller error',
-      () async {
+    testUsingContext('error if idevicescreenshot is not installed', () async {
       when(mockOutputFile.path).thenReturn(fs.path.join('some', 'test', 'path', 'image.png'));
       // Let everything else return exit code 0 so process.dart doesn't crash.
       // The matcher order is important.
@@ -65,12 +63,9 @@ void main() {
     overrides: <Type, Generator>{
       ProcessManager: () => mockProcessManager,
       Platform: () => osx,
-      }
-    );
+    });
 
-    testUsingContext(
-      'screenshot with ideviceinstaller gets command',
-      () async {
+    testUsingContext('idevicescreenshot captures and returns screenshot', () async {
       when(mockOutputFile.path).thenReturn(fs.path.join('some', 'test', 'path', 'image.png'));
       // Let everything else return exit code 0.
       // The matcher order is important.
@@ -99,8 +94,6 @@ void main() {
         environment: null,
         workingDirectory: null
       ));
-      },
-      overrides: <Type, Generator>{ProcessManager: () => mockProcessManager}
-    );
+    }, overrides: <Type, Generator>{ProcessManager: () => mockProcessManager});
   });
 }