diff --git a/lib/shared/reaction-utils.test.js b/lib/shared/reaction-utils.test.js
new file mode 100644
--- /dev/null
+++ b/lib/shared/reaction-utils.test.js
@@ -0,0 +1,114 @@
+// @flow
+
+import type { MessageReactionInfo } from '../selectors/chat-selectors';
+import { stringForReactionList } from './reaction-utils';
+
+describe(
+  'stringForReactionList(' +
+    'reactions: $ReadOnlyMap<string, MessageReactionInfo>)',
+  () => {
+    it(
+      'should return (👍 3) for a message with three user likes' +
+        'including the viewer',
+      () => {
+        const messageLikesUsers = ['83810', '86622', '83889'];
+        const messageLikesUsersSet = new Set(messageLikesUsers);
+        const messageLikesInfo = {
+          users: messageLikesUsersSet,
+          viewerReacted: true,
+        };
+
+        const reactionsMap = new Map<string, MessageReactionInfo>();
+        reactionsMap.set('👍', messageLikesInfo);
+
+        expect(stringForReactionList(reactionsMap)).toBe('👍 3');
+      },
+    );
+
+    it(
+      'should return (👍 3) for a message with three user likes' +
+        'not including the viewer',
+      () => {
+        const messageLikesUsers = ['83810', '86622', '83889'];
+        const messageLikesUsersSet = new Set(messageLikesUsers);
+        const messageLikesInfo = {
+          users: messageLikesUsersSet,
+          viewerReacted: false,
+        };
+
+        const reactionsMap = new Map<string, MessageReactionInfo>();
+        reactionsMap.set('👍', messageLikesInfo);
+
+        expect(stringForReactionList(reactionsMap)).toBe('👍 3');
+      },
+    );
+
+    it(
+      'should return (👍) for a message with one user like' +
+        'including the viewer',
+      () => {
+        const messageLikesUsers = ['83810'];
+        const messageLikesUsersSet = new Set(messageLikesUsers);
+        const messageLikesInfo = {
+          users: messageLikesUsersSet,
+          viewerReacted: true,
+        };
+
+        const reactionsMap = new Map<string, MessageReactionInfo>();
+        reactionsMap.set('👍', messageLikesInfo);
+
+        expect(stringForReactionList(reactionsMap)).toBe('👍');
+      },
+    );
+
+    it(
+      'should return (👍) for a message with one user like' +
+        'not including the viewer',
+      () => {
+        const messageLikesUsers = ['86622'];
+        const messageLikesUsersSet = new Set(messageLikesUsers);
+        const messageLikesInfo = {
+          users: messageLikesUsersSet,
+          viewerReacted: false,
+        };
+
+        const reactionsMap = new Map<string, MessageReactionInfo>();
+        reactionsMap.set('👍', messageLikesInfo);
+
+        expect(stringForReactionList(reactionsMap)).toBe('👍');
+      },
+    );
+
+    it('should return an empty string for a message no reactions', () => {
+      const reactionsMap = new Map<string, MessageReactionInfo>();
+
+      expect(stringForReactionList(reactionsMap)).toBe('');
+    });
+
+    it(
+      'should return (👍 😆 3) for a message with one like not including' +
+        'the viewer and three laugh reactions including the viewer',
+      () => {
+        const messageLikesUsers = ['86622'];
+        const messageLikesUsersSet = new Set(messageLikesUsers);
+        const messageLikesInfo = {
+          users: messageLikesUsersSet,
+          viewerReacted: false,
+        };
+
+        const messageLaughsUsers = ['12345', '67890', '83889'];
+        const messageLaughsUsersSet = new Set(messageLaughsUsers);
+        const messageLaughsInfo = {
+          users: messageLaughsUsersSet,
+          viewerReacted: true,
+        };
+
+        const reactionsMap = new Map<string, MessageReactionInfo>();
+        reactionsMap.set('👍', messageLikesInfo);
+        reactionsMap.set('😆', messageLaughsInfo);
+
+        expect(stringForReactionList(reactionsMap)).toBe('👍 😆 3');
+      },
+    );
+  },
+);