diff --git a/app/soapbox/actions/__tests__/compose.test.js b/app/soapbox/actions/__tests__/compose.test.ts
similarity index 100%
rename from app/soapbox/actions/__tests__/compose.test.js
rename to app/soapbox/actions/__tests__/compose.test.ts
diff --git a/app/soapbox/components/__tests__/autosuggest_emoji.test.js b/app/soapbox/components/__tests__/autosuggest_emoji.test.tsx
similarity index 88%
rename from app/soapbox/components/__tests__/autosuggest_emoji.test.js
rename to app/soapbox/components/__tests__/autosuggest_emoji.test.tsx
index 938ca737b..8fab0ef8b 100644
--- a/app/soapbox/components/__tests__/autosuggest_emoji.test.js
+++ b/app/soapbox/components/__tests__/autosuggest_emoji.test.tsx
@@ -10,7 +10,7 @@ describe('<AutosuggestEmoji />', () => {
       colons: ':foobar:',
     };
 
-    render(<AutosuggestEmoji emoji={emoji} />);
+    render(<AutosuggestEmoji emoji={emoji as any} />);
 
     expect(screen.getByTestId('emoji')).toHaveTextContent('foobar');
     expect(screen.getByRole('img').getAttribute('src')).not.toBe('http://example.com/emoji.png');
@@ -24,7 +24,7 @@ describe('<AutosuggestEmoji />', () => {
       colons: ':foobar:',
     };
 
-    render(<AutosuggestEmoji emoji={emoji} />);
+    render(<AutosuggestEmoji emoji={emoji as any} />);
 
     expect(screen.getByTestId('emoji')).toHaveTextContent('foobar');
     expect(screen.getByRole('img').getAttribute('src')).toBe('http://example.com/emoji.png');
diff --git a/app/soapbox/components/__tests__/avatar.test.js b/app/soapbox/components/__tests__/avatar.test.tsx
similarity index 100%
rename from app/soapbox/components/__tests__/avatar.test.js
rename to app/soapbox/components/__tests__/avatar.test.tsx
diff --git a/app/soapbox/components/__tests__/avatar_overlay.test.js b/app/soapbox/components/__tests__/avatar_overlay.test.tsx
similarity index 100%
rename from app/soapbox/components/__tests__/avatar_overlay.test.js
rename to app/soapbox/components/__tests__/avatar_overlay.test.tsx
diff --git a/app/soapbox/components/__tests__/badge.test.js b/app/soapbox/components/__tests__/badge.test.tsx
similarity index 100%
rename from app/soapbox/components/__tests__/badge.test.js
rename to app/soapbox/components/__tests__/badge.test.tsx
diff --git a/app/soapbox/components/__tests__/display_name.test.js b/app/soapbox/components/__tests__/display_name.test.tsx
similarity index 100%
rename from app/soapbox/components/__tests__/display_name.test.js
rename to app/soapbox/components/__tests__/display_name.test.tsx
diff --git a/app/soapbox/components/__tests__/emoji_selector.test.js b/app/soapbox/components/__tests__/emoji_selector.test.tsx
similarity index 100%
rename from app/soapbox/components/__tests__/emoji_selector.test.js
rename to app/soapbox/components/__tests__/emoji_selector.test.tsx
diff --git a/app/soapbox/components/__tests__/scroll-top-button.test.js b/app/soapbox/components/__tests__/scroll-top-button.test.tsx
similarity index 100%
rename from app/soapbox/components/__tests__/scroll-top-button.test.js
rename to app/soapbox/components/__tests__/scroll-top-button.test.tsx
diff --git a/app/soapbox/features/auth_login/components/__tests__/captcha.test.js b/app/soapbox/features/auth_login/components/__tests__/captcha.test.tsx
similarity index 100%
rename from app/soapbox/features/auth_login/components/__tests__/captcha.test.js
rename to app/soapbox/features/auth_login/components/__tests__/captcha.test.tsx
diff --git a/app/soapbox/features/auth_login/components/__tests__/login_form.test.js b/app/soapbox/features/auth_login/components/__tests__/login_form.test.tsx
similarity index 100%
rename from app/soapbox/features/auth_login/components/__tests__/login_form.test.js
rename to app/soapbox/features/auth_login/components/__tests__/login_form.test.tsx
diff --git a/app/soapbox/features/auth_login/components/__tests__/login_page.test.js b/app/soapbox/features/auth_login/components/__tests__/login_page.test.tsx
similarity index 100%
rename from app/soapbox/features/auth_login/components/__tests__/login_page.test.js
rename to app/soapbox/features/auth_login/components/__tests__/login_page.test.tsx
diff --git a/app/soapbox/features/emoji/emoji_picker.ts b/app/soapbox/features/emoji/emoji_picker.js
similarity index 100%
rename from app/soapbox/features/emoji/emoji_picker.ts
rename to app/soapbox/features/emoji/emoji_picker.js
diff --git a/app/soapbox/features/ui/components/__tests__/compose-button.test.js b/app/soapbox/features/ui/components/__tests__/compose-button.test.tsx
similarity index 100%
rename from app/soapbox/features/ui/components/__tests__/compose-button.test.js
rename to app/soapbox/features/ui/components/__tests__/compose-button.test.tsx
diff --git a/app/soapbox/features/ui/components/list_panel.tsx b/app/soapbox/features/ui/components/list_panel.tsx
index 14d6fc82c..8160217e9 100644
--- a/app/soapbox/features/ui/components/list_panel.tsx
+++ b/app/soapbox/features/ui/components/list_panel.tsx
@@ -15,7 +15,7 @@ const getOrderedLists = createSelector([(state: RootState) => state.lists], list
     return lists;
   }
 
-  return lists.toList().filter(item => !!item).sort((a, b) => (a as ListEntity).title.localeCompare((b as ListEntity).title)).take(4) as ImmutableList<ListEntity>;;
+  return lists.toList().filter(item => !!item).sort((a, b) => (a as ListEntity).title.localeCompare((b as ListEntity).title)).take(4) as ImmutableList<ListEntity>;
 });
 
 const ListPanel = () => {
diff --git a/app/soapbox/features/verification/steps/__tests__/age-verification.test.js b/app/soapbox/features/verification/steps/__tests__/age-verification.test.tsx
similarity index 100%
rename from app/soapbox/features/verification/steps/__tests__/age-verification.test.js
rename to app/soapbox/features/verification/steps/__tests__/age-verification.test.tsx
diff --git a/app/soapbox/features/verification/steps/__tests__/email-verification.test.js b/app/soapbox/features/verification/steps/__tests__/email-verification.test.tsx
similarity index 100%
rename from app/soapbox/features/verification/steps/__tests__/email-verification.test.js
rename to app/soapbox/features/verification/steps/__tests__/email-verification.test.tsx
diff --git a/app/soapbox/features/verification/steps/__tests__/sms-verification.test.js b/app/soapbox/features/verification/steps/__tests__/sms-verification.test.tsx
similarity index 100%
rename from app/soapbox/features/verification/steps/__tests__/sms-verification.test.js
rename to app/soapbox/features/verification/steps/__tests__/sms-verification.test.tsx
diff --git a/app/soapbox/reducers/__tests__/compose-test.js b/app/soapbox/reducers/__tests__/compose.test.ts
similarity index 96%
rename from app/soapbox/reducers/__tests__/compose-test.js
rename to app/soapbox/reducers/__tests__/compose.test.ts
index 1c4e70948..42c276cf6 100644
--- a/app/soapbox/reducers/__tests__/compose-test.js
+++ b/app/soapbox/reducers/__tests__/compose.test.ts
@@ -1,4 +1,4 @@
-import { Map as ImmutableMap, fromJS } from 'immutable';
+import { List as ImmutableList, Map as ImmutableMap, fromJS } from 'immutable';
 
 import * as actions from 'soapbox/actions/compose';
 import { ME_FETCH_SUCCESS, ME_PATCH_SUCCESS } from 'soapbox/actions/me';
@@ -220,7 +220,7 @@ describe('compose reducer', () => {
   });
 
   it('should handle COMPOSE_SPOILERNESS_CHANGE on CW button click', () => {
-    const state = ImmutableMap({ spoiler_text: 'spoiler text', spoiler: true, media_attachments: { } });
+    const state = ImmutableMap({ spoiler_text: 'spoiler text', spoiler: true, media_attachments: ImmutableList() });
     const action = {
       type: actions.COMPOSE_SPOILERNESS_CHANGE,
     };
@@ -337,7 +337,7 @@ describe('compose reducer', () => {
   });
 
   it('should handle COMPOSE_UPLOAD_SUCCESS', () => {
-    const state = ImmutableMap({ media_attachments: [] });
+    const state = ImmutableMap({ media_attachments: ImmutableList() });
     const media = [
       {
         description: null,
@@ -385,19 +385,18 @@ describe('compose reducer', () => {
   });
 
   it('should handle COMPOSE_SUGGESTIONS_CLEAR', () => {
-    const state = ImmutableMap({ });
     const action = {
       type: actions.COMPOSE_SUGGESTIONS_CLEAR,
       suggestions: [],
       suggestion_token: 'aiekdns3',
     };
-    expect(reducer(state, action).toJS()).toMatchObject({
+    expect(reducer(undefined, action).toJS()).toMatchObject({
       suggestion_token: null,
     });
   });
 
   it('should handle COMPOSE_SUGGESTION_TAGS_UPDATE', () => {
-    const state = ImmutableMap({ tagHistory: [ 'hashtag' ] });
+    const state = ImmutableMap({ tagHistory: ImmutableList([ 'hashtag' ]) });
     const action = {
       type: actions.COMPOSE_SUGGESTION_TAGS_UPDATE,
       token: 'aaadken3',
@@ -410,12 +409,11 @@ describe('compose reducer', () => {
   });
 
   it('should handle COMPOSE_TAG_HISTORY_UPDATE', () => {
-    const state = ImmutableMap({ });
     const action = {
       type: actions.COMPOSE_TAG_HISTORY_UPDATE,
       tags: [ 'hashtag', 'hashtag2'],
     };
-    expect(reducer(state, action).toJS()).toMatchObject({
+    expect(reducer(undefined, action).toJS()).toMatchObject({
       tagHistory: [ 'hashtag', 'hashtag2' ],
     });
   });
@@ -450,11 +448,10 @@ describe('compose reducer', () => {
   });
 
   it('should handle COMPOSE_POLL_REMOVE', () => {
-    const state = ImmutableMap({ });
     const action = {
       type: actions.COMPOSE_POLL_REMOVE,
     };
-    expect(reducer(state, action).toJS()).toMatchObject({
+    expect(reducer(undefined, action).toJS()).toMatchObject({
       poll: null,
     });
   });
diff --git a/app/soapbox/reducers/__tests__/contexts-test.js b/app/soapbox/reducers/__tests__/contexts.test.ts
similarity index 91%
rename from app/soapbox/reducers/__tests__/contexts-test.js
rename to app/soapbox/reducers/__tests__/contexts.test.ts
index d5270f0d8..901763091 100644
--- a/app/soapbox/reducers/__tests__/contexts-test.js
+++ b/app/soapbox/reducers/__tests__/contexts.test.ts
@@ -13,7 +13,7 @@ import reducer, { ReducerRecord } from '../contexts';
 
 describe('contexts reducer', () => {
   it('should return the initial state', () => {
-    expect(reducer(undefined, {})).toEqual(ReducerRecord({
+    expect(reducer(undefined, {} as any)).toEqual(ReducerRecord({
       inReplyTos: ImmutableMap(),
       replies: ImmutableMap(),
     }));
@@ -97,18 +97,18 @@ describe('contexts reducer', () => {
         inReplyTos: fromJS({
           B: 'A',
           C: 'B',
-        }),
+        }) as ImmutableMap<string, string>,
         replies: fromJS({
           A: ImmutableOrderedSet(['B']),
           B: ImmutableOrderedSet(['C']),
-        }),
+        }) as ImmutableMap<string, ImmutableOrderedSet<string>>,
       });
 
       const expected = ReducerRecord({
-        inReplyTos: fromJS({}),
+        inReplyTos: fromJS({}) as ImmutableMap<string, string>,
         replies: fromJS({
           A: ImmutableOrderedSet(),
-        }),
+        }) as ImmutableMap<string, ImmutableOrderedSet<string>>,
       });
 
       expect(reducer(state, action)).toEqual(expected);
diff --git a/app/soapbox/reducers/__tests__/list_adder-test.js b/app/soapbox/reducers/__tests__/list_adder.test.ts
similarity index 93%
rename from app/soapbox/reducers/__tests__/list_adder-test.js
rename to app/soapbox/reducers/__tests__/list_adder.test.ts
index 4806d3d13..3989cf5e7 100644
--- a/app/soapbox/reducers/__tests__/list_adder-test.js
+++ b/app/soapbox/reducers/__tests__/list_adder.test.ts
@@ -6,7 +6,7 @@ import reducer from '../list_adder';
 
 describe('list_adder reducer', () => {
   it('should return the initial state', () => {
-    expect(reducer(undefined, {})).toMatchObject({
+    expect(reducer(undefined, {} as any)).toMatchObject({
       accountId: null,
 
       lists: {
@@ -22,7 +22,7 @@ describe('list_adder reducer', () => {
       accountId: null,
 
       lists: ImmutableRecord({
-        items: ImmutableList(),
+        items: ImmutableList<string>(),
         loaded: false,
         isLoading: false,
       })(),
@@ -46,7 +46,7 @@ describe('list_adder reducer', () => {
       accountId: null,
 
       lists: ImmutableRecord({
-        items: ImmutableList(),
+        items: ImmutableList<string>(),
         loaded: false,
         isLoading: false,
       })(),
@@ -70,7 +70,7 @@ describe('list_adder reducer', () => {
       accountId: null,
 
       lists: ImmutableRecord({
-        items: ImmutableList(),
+        items: ImmutableList<string>(),
         loaded: false,
         isLoading: false,
       })(),
diff --git a/app/soapbox/reducers/__tests__/modals-test.js b/app/soapbox/reducers/__tests__/modals.test.ts
similarity index 56%
rename from app/soapbox/reducers/__tests__/modals-test.js
rename to app/soapbox/reducers/__tests__/modals.test.ts
index 36f4fba64..bbb5c4552 100644
--- a/app/soapbox/reducers/__tests__/modals-test.js
+++ b/app/soapbox/reducers/__tests__/modals.test.ts
@@ -1,4 +1,4 @@
-import { List as ImmutableList } from 'immutable';
+import { List as ImmutableList, Record as ImmutableRecord } from 'immutable';
 
 import { MODAL_OPEN, MODAL_CLOSE } from 'soapbox/actions/modals';
 
@@ -6,11 +6,11 @@ import reducer from '../modals';
 
 describe('modal reducer', () => {
   it('should return the initial state', () => {
-    expect(reducer(undefined, {})).toEqual(ImmutableList());
+    expect(reducer(undefined, {} as any)).toEqual(ImmutableList());
   });
 
   it('should handle MODAL_OPEN', () => {
-    const state = ImmutableList();
+    const state = ImmutableList<any>();
     const action = {
       type: MODAL_OPEN,
       modalType: 'type1',
@@ -23,35 +23,43 @@ describe('modal reducer', () => {
   });
 
   it('should handle MODAL_CLOSE', () => {
-    const state = ImmutableList([{
-      modalType: 'type1',
-      modalProps: { props1: '1' },
-    }]);
+    const state = ImmutableList([
+      ImmutableRecord({
+        modalType: 'type1',
+        modalProps: { props1: '1' },
+      })(),
+    ]);
     const action = {
       type: MODAL_CLOSE,
     };
-    expect(reducer(state, action)).toMatchObject(ImmutableList());
+    expect(reducer(state, action).toJS()).toMatchObject([]);
   });
 
   it('should handle MODAL_CLOSE with specified modalType', () => {
     const state = ImmutableList([
-      {
+      ImmutableRecord({
         modalType: 'type1',
-      },
-      {
+        modalProps: null,
+      })(),
+      ImmutableRecord({
         modalType: 'type2',
-      },
-      {
+        modalProps: null,
+      })(),
+      ImmutableRecord({
         modalType: 'type1',
-      },
+        modalProps: null,
+      })(),
     ]);
     const action = {
       type: MODAL_CLOSE,
       modalType: 'type2',
     };
-    expect(reducer(state, action)).toMatchObject(ImmutableList([{
-      modalType: 'type1',
-    }]));
+    expect(reducer(state, action).toJS()).toEqual([
+      {
+        modalType: 'type1',
+        modalProps: null,
+      },
+    ]);
   });
 
 });
diff --git a/app/soapbox/reducers/__tests__/mutes.test.ts b/app/soapbox/reducers/__tests__/mutes.test.ts
index 512a5260f..411db10c6 100644
--- a/app/soapbox/reducers/__tests__/mutes.test.ts
+++ b/app/soapbox/reducers/__tests__/mutes.test.ts
@@ -42,6 +42,8 @@ describe('mutes reducer', () => {
   it('should handle MUTES_TOGGLE_HIDE_NOTIFICATIONS', () => {
     const state = ImmutableRecord({
       new: ImmutableRecord({
+        isSubmitting: false,
+        accountId: null,
         notifications: true,
       })(),
     })();
@@ -50,6 +52,8 @@ describe('mutes reducer', () => {
     };
     expect(reducer(state, action).toJS()).toEqual({
       new: {
+        isSubmitting: false,
+        accountId: null,
         notifications: false,
       },
     });
diff --git a/app/soapbox/utils/__tests__/config_db-test.js b/app/soapbox/utils/__tests__/config_db.test.ts
similarity index 61%
rename from app/soapbox/utils/__tests__/config_db-test.js
rename to app/soapbox/utils/__tests__/config_db.test.ts
index b8ad15e0f..a83757eb3 100644
--- a/app/soapbox/utils/__tests__/config_db-test.js
+++ b/app/soapbox/utils/__tests__/config_db.test.ts
@@ -1,4 +1,4 @@
-import { fromJS } from 'immutable';
+import { List as ImmutableList, fromJS } from 'immutable';
 
 import config_db from 'soapbox/__fixtures__/config_db.json';
 
@@ -6,7 +6,7 @@ import { ConfigDB } from '../config_db';
 
 test('find', () => {
   const configs = fromJS(config_db).get('configs');
-  expect(ConfigDB.find(configs, ':phoenix', ':json_library')).toEqual(fromJS({
+  expect(ConfigDB.find(configs as ImmutableList<any>, ':phoenix', ':json_library')).toEqual(fromJS({
     group: ':phoenix',
     key: ':json_library',
     value: 'Jason',
diff --git a/app/soapbox/utils/__tests__/numbers-test.tsx b/app/soapbox/utils/__tests__/numbers.test.tsx
similarity index 100%
rename from app/soapbox/utils/__tests__/numbers-test.tsx
rename to app/soapbox/utils/__tests__/numbers.test.tsx