1 files changed, 149 insertions, 0 deletions
diff --git a/spec/frontend/mocks/mocks_helper_spec.js b/spec/frontend/mocks/mocks_helper_spec.js
new file mode 100644
index 00000000000..b8bb02c2f43
--- /dev/null
+++ b/spec/frontend/mocks/mocks_helper_spec.js
@@ -0,0 +1,149 @@
+/* eslint-disable global-require, promise/catch-or-return */
+
+import path from 'path';
+
+import axios from '~/lib/utils/axios_utils';
+
+const absPath = path.join.bind(null, __dirname);
+
+jest.mock('fs');
+jest.mock('readdir-enhanced');
+
+describe('mocks_helper.js', () => {
+  let setupManualMocks;
+  const setMock = jest.fn().mockName('setMock');
+  let fs;
+  let readdir;
+
+  beforeAll(() => {
+    jest.resetModules();
+    jest.setMock = jest.fn().mockName('jest.setMock');
+    fs = require('fs');
+    readdir = require('readdir-enhanced');
+
+    // We need to provide setupManualMocks with a mock function that pretends to do the setup of
+    // the mock. This is because we can't mock jest.setMock across files.
+    setupManualMocks = () => require('./mocks_helper').setupManualMocks(setMock);
+  });
+
+  afterEach(() => {
+    fs.existsSync.mockReset();
+    readdir.sync.mockReset();
+    setMock.mockReset();
+  });
+
+  it('enumerates through mock file roots', () => {
+    setupManualMocks();
+    expect(fs.existsSync).toHaveBeenCalledTimes(2);
+    expect(fs.existsSync).toHaveBeenNthCalledWith(1, absPath('ce'));
+    expect(fs.existsSync).toHaveBeenNthCalledWith(2, absPath('node'));
+
+    expect(readdir.sync).toHaveBeenCalledTimes(0);
+  });
+
+  it("doesn't traverse the directory tree infinitely", () => {
+    fs.existsSync.mockReturnValue(true);
+    readdir.sync.mockReturnValue([]);
+    setupManualMocks();
+
+    const readdirSpy = readdir.sync;
+    expect(readdirSpy).toHaveBeenCalled();
+    readdirSpy.mock.calls.forEach(call => {
+      expect(call[1].deep).toBeLessThan(100);
+    });
+  });
+
+  it('sets up mocks for CE (the ~/ prefix)', () => {
+    fs.existsSync.mockImplementation(root => root.endsWith('ce'));
+    readdir.sync.mockReturnValue(['root.js', 'lib/utils/util.js']);
+    setupManualMocks();
+
+    expect(readdir.sync).toHaveBeenCalledTimes(1);
+    expect(readdir.sync.mock.calls[0][0]).toBe(absPath('ce'));
+
+    expect(setMock).toHaveBeenCalledTimes(2);
+    expect(setMock).toHaveBeenNthCalledWith(1, '~/root', './ce/root');
+    expect(setMock).toHaveBeenNthCalledWith(2, '~/lib/utils/util', './ce/lib/utils/util');
+  });
+
+  it('sets up mocks for node_modules', () => {
+    fs.existsSync.mockImplementation(root => root.endsWith('node'));
+    readdir.sync.mockReturnValue(['jquery', '@babel/core']);
+    setupManualMocks();
+
+    expect(readdir.sync).toHaveBeenCalledTimes(1);
+    expect(readdir.sync.mock.calls[0][0]).toBe(absPath('node'));
+
+    expect(setMock).toHaveBeenCalledTimes(2);
+    expect(setMock).toHaveBeenNthCalledWith(1, 'jquery', './node/jquery');
+    expect(setMock).toHaveBeenNthCalledWith(2, '@babel/core', './node/@babel/core');
+  });
+
+  it('sets up mocks for all roots', () => {
+    const files = {
+      [absPath('ce')]: ['root', 'lib/utils/util'],
+      [absPath('node')]: ['jquery', '@babel/core'],
+    };
+
+    fs.existsSync.mockReturnValue(true);
+    readdir.sync.mockImplementation(root => files[root]);
+    setupManualMocks();
+
+    expect(readdir.sync).toHaveBeenCalledTimes(2);
+    expect(readdir.sync.mock.calls[0][0]).toBe(absPath('ce'));
+    expect(readdir.sync.mock.calls[1][0]).toBe(absPath('node'));
+
+    expect(setMock).toHaveBeenCalledTimes(4);
+    expect(setMock).toHaveBeenNthCalledWith(1, '~/root', './ce/root');
+    expect(setMock).toHaveBeenNthCalledWith(2, '~/lib/utils/util', './ce/lib/utils/util');
+    expect(setMock).toHaveBeenNthCalledWith(3, 'jquery', './node/jquery');
+    expect(setMock).toHaveBeenNthCalledWith(4, '@babel/core', './node/@babel/core');
+  });
+
+  it('fails when given a virtual mock', () => {
+    fs.existsSync.mockImplementation(p => p.endsWith('ce'));
+    readdir.sync.mockReturnValue(['virtual', 'shouldntBeImported']);
+    setMock.mockImplementation(() => {
+      throw new Error('Could not locate module');
+    });
+
+    expect(setupManualMocks).toThrow(
+      new Error("A manual mock was defined for module ~/virtual, but the module doesn't exist!"),
+    );
+
+    expect(readdir.sync).toHaveBeenCalledTimes(1);
+    expect(readdir.sync.mock.calls[0][0]).toBe(absPath('ce'));
+  });
+
+  describe('auto-injection', () => {
+    it('handles ambiguous paths', () => {
+      jest.isolateModules(() => {
+        const axios2 = require('../../../app/assets/javascripts/lib/utils/axios_utils').default;
+        expect(axios2.isMock).toBe(true);
+      });
+    });
+
+    it('survives jest.isolateModules()', done => {
+      jest.isolateModules(() => {
+        const axios2 = require('~/lib/utils/axios_utils').default;
+        expect(axios2.get('http://gitlab.com'))
+          .rejects.toThrow('Unexpected unmocked request')
+          .then(done);
+      });
+    });
+
+    it('can be unmocked and remocked', () => {
+      jest.dontMock('~/lib/utils/axios_utils');
+      jest.resetModules();
+      const axios2 = require('~/lib/utils/axios_utils').default;
+      expect(axios2).not.toBe(axios);
+      expect(axios2.isMock).toBeUndefined();
+
+      jest.doMock('~/lib/utils/axios_utils');
+      jest.resetModules();
+      const axios3 = require('~/lib/utils/axios_utils').default;
+      expect(axios3).not.toBe(axios2);
+      expect(axios3.isMock).toBe(true);
+    });
+  });
+});