diff --git a/app/components/combined_system_message/combined_system_message.test.js b/app/components/combined_system_message/combined_system_message.test.js
index 27390fbc5..496c7d493 100644
--- a/app/components/combined_system_message/combined_system_message.test.js
+++ b/app/components/combined_system_message/combined_system_message.test.js
@@ -7,15 +7,19 @@ import Adapter from 'enzyme-adapter-react-16';
 configure({adapter: new Adapter()});
 
 import {shallowWithIntl} from 'test/intl-test-helper';
+import {emptyFunction} from 'app/utils/general';
 
 import {Posts} from 'mattermost-redux/constants';
 
 import CombinedSystemMessage from './combined_system_message';
 
+/* eslint-disable max-nested-callbacks, no-console */
+
 describe('CombinedSystemMessage', () => {
     const baseProps = {
         actions: {
-            getProfilesByIds: () => {}, // eslint-disable-line no-empty-function
+            getProfilesByIds: emptyFunction,
+            getProfilesByUsernames: emptyFunction,
         },
         allUserIds: ['user_id_1', 'user_id_2', 'user_id_3'],
         currentUserId: 'user_id_3',
@@ -31,7 +35,10 @@ describe('CombinedSystemMessage', () => {
     test('should match snapshot', () => {
         const props = {
             ...baseProps,
-            actions: {getProfilesByIds: jest.fn(() => Promise.resolve({data: true}))},
+            actions: {
+                getProfilesByIds: jest.fn(() => Promise.resolve({data: true})),
+                getProfilesByUsernames: emptyFunction,
+            },
         };
         const wrapper = shallowWithIntl(
             <CombinedSystemMessage {...props}/>
@@ -49,7 +56,10 @@ describe('CombinedSystemMessage', () => {
     test('should match snapshot', () => {
         const props = {
             ...baseProps,
-            actions: {getProfilesByIds: jest.fn(() => Promise.resolve({data: true}))},
+            actions: {
+                getProfilesByIds: jest.fn(() => Promise.resolve({data: true})),
+                getProfilesByUsernames: emptyFunction,
+            },
         };
         const localeFormat = {
             id: ['combined_system_message.first_user_and_second_user_were', 'combined_system_message.removed_from_team'],
diff --git a/app/components/custom_list/__snapshots__/index.test.js.snap b/app/components/custom_list/__snapshots__/index.test.js.snap
new file mode 100644
index 000000000..851c7ac81
--- /dev/null
+++ b/app/components/custom_list/__snapshots__/index.test.js.snap
@@ -0,0 +1,273 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`CustomList should match snapshot 1`] = `
+ShallowWrapper {
+  "length": 1,
+  Symbol(enzyme.__root__): [Circular],
+  Symbol(enzyme.__unrendered__): <CustomList
+    createSections={[Function]}
+    data={
+      Array [
+        Object {
+          "username": "username_1",
+        },
+        Object {
+          "username": "username_2",
+        },
+      ]
+    }
+    listInitialSize={0}
+    listPageSize={0}
+    listScrollRenderAheadDistance={0}
+    loading={false}
+    loadingText={
+      Object {
+        "defaultMessage": "Loading Members...",
+        "id": "mobile.loading_members",
+      }
+    }
+    onListEndReached={[Function]}
+    onListEndReachedThreshold={0}
+    onRowPress={[Function]}
+    onRowSelect={[Function]}
+    renderRow={[Function]}
+    searching={false}
+    selectable={true}
+    showNoResults={false}
+    showSections={true}
+    theme={
+      Object {
+        "centerChannelBg": "#aaa",
+        "centerChannelColor": "#aaa",
+      }
+    }
+  />,
+  Symbol(enzyme.__renderer__): Object {
+    "batchedUpdates": [Function],
+    "getNode": [Function],
+    "render": [Function],
+    "simulateEvent": [Function],
+    "unmount": [Function],
+  },
+  Symbol(enzyme.__node__): Object {
+    "instance": null,
+    "key": undefined,
+    "nodeType": "class",
+    "props": Object {
+      "children": Array [
+        <ListViewMock
+          dataSource={
+            ListViewDataSource {
+              "items": 2,
+            }
+          }
+          enableEmptySections={true}
+          initialListSize={0}
+          onEndReached={[Function]}
+          onEndReachedThreshold={0}
+          pageSize={0}
+          renderFooter={[Function]}
+          renderRow={[Function]}
+          renderScrollComponent={[Function]}
+          renderSectionHeader={[Function]}
+          renderSeparator={[Function]}
+          scrollRenderAheadDistance={0}
+          style={
+            Object {
+              "backgroundColor": "#aaa",
+              "flex": 1,
+            }
+          }
+        />,
+        undefined,
+      ],
+      "style": Object {
+        "flex": 1,
+      },
+    },
+    "ref": null,
+    "rendered": Array [
+      Object {
+        "instance": null,
+        "key": undefined,
+        "nodeType": "class",
+        "props": Object {
+          "dataSource": ListViewDataSource {
+            "items": 2,
+          },
+          "enableEmptySections": true,
+          "initialListSize": 0,
+          "onEndReached": [Function],
+          "onEndReachedThreshold": 0,
+          "pageSize": 0,
+          "renderFooter": [Function],
+          "renderRow": [Function],
+          "renderScrollComponent": [Function],
+          "renderSectionHeader": [Function],
+          "renderSeparator": [Function],
+          "scrollRenderAheadDistance": 0,
+          "style": Object {
+            "backgroundColor": "#aaa",
+            "flex": 1,
+          },
+        },
+        "ref": null,
+        "rendered": null,
+        "type": [Function],
+      },
+      undefined,
+    ],
+    "type": [Function],
+  },
+  Symbol(enzyme.__nodes__): Array [
+    Object {
+      "instance": null,
+      "key": undefined,
+      "nodeType": "class",
+      "props": Object {
+        "children": Array [
+          <ListViewMock
+            dataSource={
+              ListViewDataSource {
+                "items": 2,
+              }
+            }
+            enableEmptySections={true}
+            initialListSize={0}
+            onEndReached={[Function]}
+            onEndReachedThreshold={0}
+            pageSize={0}
+            renderFooter={[Function]}
+            renderRow={[Function]}
+            renderScrollComponent={[Function]}
+            renderSectionHeader={[Function]}
+            renderSeparator={[Function]}
+            scrollRenderAheadDistance={0}
+            style={
+              Object {
+                "backgroundColor": "#aaa",
+                "flex": 1,
+              }
+            }
+          />,
+          undefined,
+        ],
+        "style": Object {
+          "flex": 1,
+        },
+      },
+      "ref": null,
+      "rendered": Array [
+        Object {
+          "instance": null,
+          "key": undefined,
+          "nodeType": "class",
+          "props": Object {
+            "dataSource": ListViewDataSource {
+              "items": 2,
+            },
+            "enableEmptySections": true,
+            "initialListSize": 0,
+            "onEndReached": [Function],
+            "onEndReachedThreshold": 0,
+            "pageSize": 0,
+            "renderFooter": [Function],
+            "renderRow": [Function],
+            "renderScrollComponent": [Function],
+            "renderSectionHeader": [Function],
+            "renderSeparator": [Function],
+            "scrollRenderAheadDistance": 0,
+            "style": Object {
+              "backgroundColor": "#aaa",
+              "flex": 1,
+            },
+          },
+          "ref": null,
+          "rendered": null,
+          "type": [Function],
+        },
+        undefined,
+      ],
+      "type": [Function],
+    },
+  ],
+  Symbol(enzyme.__options__): Object {
+    "adapter": ReactSixteenAdapter {
+      "options": Object {
+        "enableComponentDidUpdateOnSetState": true,
+      },
+    },
+  },
+}
+`;
+
+exports[`CustomList should match snapshot, renderFooter 1`] = `null`;
+
+exports[`CustomList should match snapshot, renderFooter 2`] = `
+<Component
+  style={
+    Object {
+      "alignItems": "center",
+      "backgroundColor": "#aaa",
+      "height": 70,
+      "justifyContent": "center",
+    }
+  }
+>
+  <InjectIntl(FormattedText)
+    defaultMessage="Loading Members..."
+    id="mobile.loading_members"
+    style={
+      Object {
+        "color": "rgba(170,170,170,0.6)",
+      }
+    }
+  />
+</Component>
+`;
+
+exports[`CustomList should match snapshot, renderSectionHeader 1`] = `
+<Component
+  style={
+    Object {
+      "backgroundColor": "#aaa",
+    }
+  }
+>
+  <Component
+    style={
+      Object {
+        "backgroundColor": "rgba(170,170,170,0.07)",
+        "paddingLeft": 10,
+        "paddingVertical": 2,
+      }
+    }
+  >
+    <Text
+      accessible={true}
+      allowFontScaling={true}
+      ellipsizeMode="tail"
+      style={
+        Object {
+          "color": "#aaa",
+          "fontWeight": "600",
+        }
+      }
+    >
+      section_id
+    </Text>
+  </Component>
+</Component>
+`;
+
+exports[`CustomList should match snapshot, renderSeparator 1`] = `
+<Component
+  style={
+    Object {
+      "backgroundColor": "rgba(170,170,170,0.1)",
+      "flex": 1,
+      "height": 1,
+    }
+  }
+/>
+`;
diff --git a/app/components/custom_list/index.js b/app/components/custom_list/index.js
index f204472dd..039dbfcfa 100644
--- a/app/components/custom_list/index.js
+++ b/app/components/custom_list/index.js
@@ -60,10 +60,9 @@ export default class CustomList extends PureComponent {
                 newData = this.props.createSections(data);
             }
 
-            const mergedData = Object.assign({}, newData, this.state.data);
-            const dataSource = showSections ? this.state.dataSource.cloneWithRowsAndSections(mergedData) : this.state.dataSource.cloneWithRows(mergedData);
+            const dataSource = showSections ? this.state.dataSource.cloneWithRowsAndSections(newData) : this.state.dataSource.cloneWithRows(newData);
             this.setState({
-                data: mergedData,
+                data: newData,
                 dataSource,
             });
         }
diff --git a/app/components/custom_list/index.test.js b/app/components/custom_list/index.test.js
new file mode 100644
index 000000000..0df1be395
--- /dev/null
+++ b/app/components/custom_list/index.test.js
@@ -0,0 +1,100 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See License.txt for license information.
+
+import React from 'react';
+import {configure, shallow} from 'enzyme';
+import Adapter from 'enzyme-adapter-react-16';
+configure({adapter: new Adapter()});
+
+import {createMembersSections, loadingText} from 'app/utils/member_list';
+
+import CustomList from './index';
+
+describe('CustomList', () => {
+    function emptyFunc() {} // eslint-disable-line no-empty-function
+
+    const baseProps = {
+        data: [{username: 'username_1'}, {username: 'username_2'}],
+        theme: {centerChannelBg: '#aaa', centerChannelColor: '#aaa'},
+        searching: false,
+        onListEndReached: emptyFunc,
+        onListEndReachedThreshold: 0,
+        loading: false,
+        loadingText,
+        listPageSize: 0,
+        listInitialSize: 0,
+        listScrollRenderAheadDistance: 0,
+        showSections: true,
+        onRowPress: emptyFunc,
+        selectable: true,
+        onRowSelect: emptyFunc,
+        renderRow: emptyFunc,
+        createSections: createMembersSections,
+        showNoResults: false,
+    };
+
+    test('should match snapshot', () => {
+        const wrapper = shallow(
+            <CustomList {...baseProps}/>
+        );
+        expect(wrapper).toMatchSnapshot();
+        expect(wrapper.state('data')).toEqual({U: baseProps.data});
+
+        // on componentWillReceiveProps
+        const newDataProps = [{username: 'username_1'}, {username: 'username_2'}, {username: 'username_3'}];
+        wrapper.setProps({data: newDataProps});
+        expect(wrapper.state('data')).toEqual({U: newDataProps});
+    });
+
+    test('should match return value on buildDataSource', () => {
+        const props = {...baseProps};
+        const wrapper = shallow(
+            <CustomList {...props}/>
+        );
+
+        expect(wrapper.instance().buildDataSource(props).data).toEqual({U: [{username: 'username_1'}, {username: 'username_2'}]});
+        const newDataProps = [{username: 'aaa_1'}, {username: 'aaa_2'}, {username: 'username_1'}, {username: 'username_2'}, {username: 'username_3'}];
+        props.data = newDataProps;
+        expect(wrapper.instance().buildDataSource(props).data).toEqual({
+            A: [{username: 'aaa_1'}, {username: 'aaa_2'}],
+            U: [{username: 'username_1'}, {username: 'username_2'}, {username: 'username_3'}],
+        });
+    });
+
+    test('should match snapshot, renderSectionHeader', () => {
+        const wrapper = shallow(
+            <CustomList {...baseProps}/>
+        );
+        expect(wrapper.instance().renderSectionHeader([], 'section_id')).toMatchSnapshot();
+    });
+
+    test('should call props.renderRow on renderRow', () => {
+        const props = {...baseProps, renderRow: jest.fn()};
+        const wrapper = shallow(
+            <CustomList {...props}/>
+        );
+        wrapper.instance().renderRow({id: 'item_id', selected: true}, 'section_id', 'row_id');
+        expect(props.renderRow).toHaveBeenCalledTimes(1);
+    });
+
+    test('should match snapshot, renderSeparator', () => {
+        const wrapper = shallow(
+            <CustomList {...baseProps}/>
+        );
+        expect(wrapper.instance().renderSeparator('section_id', 'row_id')).toMatchSnapshot();
+    });
+
+    test('should match snapshot, renderFooter', () => {
+        const props = {...baseProps};
+        const wrapper = shallow(
+            <CustomList {...props}/>
+        );
+
+        // should return null
+        expect(wrapper.instance().renderFooter()).toMatchSnapshot();
+
+        // should return element
+        wrapper.setProps({loading: true});
+        expect(wrapper.instance().renderFooter()).toMatchSnapshot();
+    });
+});