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 +1,90 @@
+// @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');
+  });
+});