unit test missing section-controller fix

Summary: Lets test that the new updater (`IGListExperimentalAdapterUpdater`) can handle a missing section-controller. The old adapater `IGListAdapterUpdater` would crash.

Reviewed By: patters

Differential Revision: D23145773

fbshipit-source-id: 4589dcb11ddef5c7400947aea4b6827f1b2caaa8

Tests/IGListExperimentalAdapterE2ETests.m

@@ -1976,4 +1976,30 @@
     [self waitForExpectationsWithTimeout:30 handler:nil];
 }
 
+- (void)test_whenUpdating_withMissingSectionController_thatDoesNotCrash {
+    [self setupWithObjects:@[
+        genTestObject(@0, @"Foo"),
+        genTestObject(@1, @"Bar")
+    ]];
+    
+    // Adding an object that won't have a corresponding section-controller
+    self.dataSource.objects = @[
+        genTestObject(@0, @"Foo"),
+        genTestObject(@1, @"Bar"),
+        kIGTestDelegateDataSourceSkipObject
+    ];
+    
+    // Perform updates on the adapter
+    XCTestExpectation *expectation = genExpectation;
+    [self.adapter performUpdatesAnimated:NO completion:^(BOOL finished) {
+        // Checked that the update worked
+        XCTAssertTrue(finished);
+        // Check that we skipped the object with a missing section-controller
+        XCTAssertEqual([self.collectionView numberOfSections], 2);
+        XCTAssertEqual(self.adapter.objects.count, 2);
+        [expectation fulfill];
+    }];
+    [self waitForExpectationsWithTimeout:30 handler:nil];
+}
+
 @end

Tests/Objects/IGTestDelegateDataSource.h

@@ -14,6 +14,8 @@
 @class IGTestDelegateController;
 @class IGTestObject;
 
+extern NSObject *const kIGTestDelegateDataSourceSkipObject;
+
 @interface IGTestDelegateDataSource : NSObject <IGListTestCaseDataSource>
 
 @property (nonatomic, copy) NSArray <IGTestObject *> *objects;

Tests/Objects/IGTestDelegateDataSource.m

@@ -12,6 +12,8 @@
 #import "IGTestDelegateController.h"
 #import "IGTestObject.h"
 
+NSObject *const kIGTestDelegateDataSourceSkipObject = @"kIGTestDelegateDataSourceSkipObject";
+
 @implementation IGTestDelegateDataSource
 
 - (NSArray *)objectsForListAdapter:(IGListAdapter *)listAdapter {
@@ -19,6 +21,9 @@
 }
 
 - (IGListSectionController *)listAdapter:(IGListAdapter *)listAdapter sectionControllerForObject:(id)object {
+    if ([object isEqual:kIGTestDelegateDataSourceSkipObject]) {
+        return nil;
+    }
     IGTestDelegateController *sectionController = [[IGTestDelegateController alloc] init];
     sectionController.cellConfigureBlock = self.cellConfigureBlock;
     return sectionController;