diff --git a/static_src/reducers/users.test.js b/static_src/reducers/users.test.js
new file mode 100644
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--- /dev/null
+++ b/static_src/reducers/users.test.js
@@ -0,0 +1,178 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import {assert} from 'chai';
+import sinon from 'sinon';
+
+import * as users from './users.js';
+import * as example from 'shared/test/constants-users.js';
+
+import {prpcClient} from 'prpc-client-instance.js';
+
+let dispatch;
+
+describe('user reducers', () => {
+  it('root reducer initial state', () => {
+    const actual = users.reducer(undefined, {type: null});
+    const expected = {
+      currentUserName: null,
+      byName: {},
+      projectMemberships: {},
+      requests: {
+        batchGet: {},
+        fetch: {},
+        gatherProjectMemberships: {},
+      },
+    };
+    assert.deepEqual(actual, expected);
+  });
+
+  it('currentUserName updates on LOG_IN', () => {
+    const action = {type: users.LOG_IN, user: example.USER};
+    const actual = users.currentUserNameReducer(null, action);
+    assert.deepEqual(actual, example.NAME);
+  });
+
+  it('byName updates on BATCH_GET_SUCCESS', () => {
+    const action = {type: users.BATCH_GET_SUCCESS, users: [example.USER]};
+    const actual = users.byNameReducer({}, action);
+    assert.deepEqual(actual, {[example.NAME]: example.USER});
+  });
+
+  describe('projectMembershipsReducer', () => {
+    it('updates on GATHER_PROJECT_MEMBERSHIPS_SUCCESS', () => {
+      const action = {type: users.GATHER_PROJECT_MEMBERSHIPS_SUCCESS,
+        userName: example.NAME, projectMemberships: [example.PROJECT_MEMBER]};
+      const actual = users.projectMembershipsReducer({}, action);
+      assert.deepEqual(actual, {[example.NAME]: [example.PROJECT_MEMBER]});
+    });
+
+    it('sets empty on GATHER_PROJECT_MEMBERSHIPS_SUCCESS', () => {
+      const action = {type: users.GATHER_PROJECT_MEMBERSHIPS_SUCCESS,
+        userName: example.NAME, projectMemberships: undefined};
+      const actual = users.projectMembershipsReducer({}, action);
+      assert.deepEqual(actual, {[example.NAME]: []});
+    });
+  });
+});
+
+describe('user selectors', () => {
+  it('currentUserName', () => {
+    const state = {users: {currentUserName: example.NAME}};
+    assert.deepEqual(users.currentUserName(state), example.NAME);
+  });
+
+  it('byName', () => {
+    const state = {users: {byName: example.BY_NAME}};
+    assert.deepEqual(users.byName(state), example.BY_NAME);
+  });
+
+  it('projectMemberships', () => {
+    const membershipsByName = {[example.NAME]: [example.PROJECT_MEMBER]};
+    const state = {users: {projectMemberships: membershipsByName}};
+    assert.deepEqual(users.projectMemberships(state), membershipsByName);
+  });
+});
+
+describe('user action creators', () => {
+  beforeEach(() => {
+    sinon.stub(prpcClient, 'call');
+    dispatch = sinon.stub();
+  });
+
+  afterEach(() => {
+    prpcClient.call.restore();
+  });
+
+  describe('batchGet', () => {
+    it('success', async () => {
+      prpcClient.call.returns(Promise.resolve({users: [example.USER]}));
+
+      await users.batchGet([example.NAME])(dispatch);
+
+      sinon.assert.calledWith(dispatch, {type: users.BATCH_GET_START});
+
+      const args = {names: [example.NAME]};
+      sinon.assert.calledWith(
+          prpcClient.call, 'monorail.v3.Users', 'BatchGetUsers', args);
+
+      const action = {type: users.BATCH_GET_SUCCESS, users: [example.USER]};
+      sinon.assert.calledWith(dispatch, action);
+    });
+
+    it('failure', async () => {
+      prpcClient.call.throws();
+
+      await users.batchGet([example.NAME])(dispatch);
+
+      const action = {type: users.BATCH_GET_FAILURE, error: sinon.match.any};
+      sinon.assert.calledWith(dispatch, action);
+    });
+  });
+
+  describe('fetch', () => {
+    it('success', async () => {
+      prpcClient.call.returns(Promise.resolve(example.USER));
+
+      await users.fetch(example.NAME)(dispatch);
+
+      sinon.assert.calledWith(dispatch, {type: users.FETCH_START});
+
+      const args = {name: example.NAME};
+      sinon.assert.calledWith(
+          prpcClient.call, 'monorail.v3.Users', 'GetUser', args);
+
+      const fetchAction = {type: users.FETCH_SUCCESS, user: example.USER};
+      sinon.assert.calledWith(dispatch, fetchAction);
+
+      const logInAction = {type: users.LOG_IN, user: example.USER};
+      sinon.assert.calledWith(dispatch, logInAction);
+    });
+
+    it('failure', async () => {
+      prpcClient.call.throws();
+
+      await users.fetch(example.NAME)(dispatch);
+
+      const action = {type: users.FETCH_FAILURE, error: sinon.match.any};
+      sinon.assert.calledWith(dispatch, action);
+    });
+  });
+
+  describe('gatherProjectMemberships', () => {
+    it('success', async () => {
+      prpcClient.call.returns(Promise.resolve({projectMemberships: [
+        example.PROJECT_MEMBER,
+      ]}));
+
+      await users.gatherProjectMemberships(
+          example.NAME)(dispatch);
+
+      sinon.assert.calledWith(dispatch,
+          {type: users.GATHER_PROJECT_MEMBERSHIPS_START});
+
+      const args = {user: example.NAME};
+      sinon.assert.calledWith(
+          prpcClient.call, 'monorail.v3.Frontend',
+          'GatherProjectMembershipsForUser', args);
+
+      const action = {
+        type: users.GATHER_PROJECT_MEMBERSHIPS_SUCCESS,
+        projectMemberships: [example.PROJECT_MEMBER],
+        userName: example.NAME,
+      };
+      sinon.assert.calledWith(dispatch, action);
+    });
+
+    it('failure', async () => {
+      prpcClient.call.throws(new Error());
+
+      await users.batchGet([example.NAME])(dispatch);
+
+      const action = {type: users.BATCH_GET_FAILURE,
+        error: sinon.match.instanceOf(Error)};
+      sinon.assert.calledWith(dispatch, action);
+    });
+  });
+});