emoji test: Add tests for emojiDisplayFor

Now that this logic has been pulled out to model code, we can
more easily write tests for it.

Author: gnprice

test/model/emoji_test.dart

@@ -0,0 +1,89 @@
+import 'package:checks/checks.dart';
+import 'package:test/scaffolding.dart';
+import 'package:zulip/api/model/model.dart';
+import 'package:zulip/model/emoji.dart';
+
+import '../example_data.dart' as eg;
+
+void main() {
+  group('emojiDisplayFor', () {
+    test('Unicode emoji', () {
+      check(eg.store().emojiDisplayFor(emojiType: ReactionType.unicodeEmoji,
+        emojiCode: '1f642', emojiName: 'smile')
+      ).isA<UnicodeEmojiDisplay>()
+        ..emojiName.equals('smile')
+        ..emojiUnicode.equals('🙂');
+    });
+
+    test('invalid Unicode emoji -> no crash', () {
+      check(eg.store().emojiDisplayFor(emojiType: ReactionType.unicodeEmoji,
+        emojiCode: 'asdf', emojiName: 'invalid')
+      ).isA<TextEmojiDisplay>()
+        .emojiName.equals('invalid');
+    });
+
+    test('realm emoji', () {
+      final store = eg.store(initialSnapshot: eg.initialSnapshot(realmEmoji: {
+        '100': eg.realmEmojiItem(emojiCode: '100', emojiName: 'logo',
+            sourceUrl: '/emoji/100.png'),
+        '123': eg.realmEmojiItem(emojiCode: '123', emojiName: '100',
+            sourceUrl: '/emoji/123.png'),
+        '200': eg.realmEmojiItem(emojiCode: '200', emojiName: 'dancing',
+            sourceUrl: '/emoji/200.png', stillUrl: '/emoji/200-still.png'),
+      }));
+
+      Subject<EmojiDisplay> checkDisplay({
+          required String emojiCode, required String emojiName}) {
+        return check(store.emojiDisplayFor(emojiType: ReactionType.realmEmoji,
+          emojiCode: emojiCode, emojiName: emojiName)
+        )..emojiName.equals(emojiName);
+      }
+
+      checkDisplay(emojiCode: '100', emojiName: 'logo').isA<ImageEmojiDisplay>()
+        ..resolvedUrl.equals(eg.realmUrl.resolve('/emoji/100.png'))
+        ..resolvedStillUrl.isNull();
+
+      // Emoji code matches against emoji code, not against emoji name.
+      checkDisplay(emojiCode: '123', emojiName: '100').isA<ImageEmojiDisplay>()
+        ..resolvedUrl.equals(eg.realmUrl.resolve('/emoji/123.png'))
+        ..resolvedStillUrl.isNull();
+
+      // Unexpected name is accepted.
+      checkDisplay(emojiCode: '100', emojiName: 'other').isA<ImageEmojiDisplay>()
+        ..resolvedUrl.equals(eg.realmUrl.resolve('/emoji/100.png'))
+        ..resolvedStillUrl.isNull();
+
+      // Unexpected code falls back to text.
+      checkDisplay(emojiCode: '99', emojiName: 'another')
+        .isA<TextEmojiDisplay>();
+
+      checkDisplay(emojiCode: '200', emojiName: 'dancing').isA<ImageEmojiDisplay>()
+        ..resolvedUrl.equals(eg.realmUrl.resolve('/emoji/200.png'))
+        ..resolvedStillUrl.equals(eg.realmUrl.resolve('/emoji/200-still.png'));
+
+      // TODO test URLs not parsing
+    });
+
+    test(':zulip:', () {
+      check(eg.store().emojiDisplayFor(emojiType: ReactionType.zulipExtraEmoji,
+        emojiCode: 'zulip', emojiName: 'zulip')
+      ).isA<ImageEmojiDisplay>()
+        ..emojiName.equals('zulip')
+        ..resolvedUrl.equals(eg.realmUrl.resolve(EmojiStoreImpl.kZulipEmojiUrl))
+        ..resolvedStillUrl.isNull();
+    });
+  });
+}
+
+extension EmojiDisplayChecks on Subject<EmojiDisplay> {
+  Subject<String> get emojiName => has((x) => x.emojiName, 'emojiName');
+}
+
+extension UnicodeEmojiDisplayChecks on Subject<UnicodeEmojiDisplay> {
+  Subject<String> get emojiUnicode => has((x) => x.emojiUnicode, 'emojiUnicode');
+}
+
+extension ImageEmojiDisplayChecks on Subject<ImageEmojiDisplay> {
+  Subject<Uri> get resolvedUrl => has((x) => x.resolvedUrl, 'resolvedUrl');
+  Subject<Uri?> get resolvedStillUrl => has((x) => x.resolvedStillUrl, 'resolvedStillUrl');
+}