test: migrate is-docker to jest

test/jest/unit/is-docker.spec.ts

@@ -0,0 +1,56 @@
+import * as fs from 'fs';
+import * as path from 'path';
+
+import { isDocker } from '../../../src/lib/is-docker';
+
+describe('isDocker', () => {
+  afterEach(() => {
+    jest.restoreAllMocks();
+  });
+
+  it('inside a Docker container (.dockerenv test)', async () => {
+    delete require.cache[path.join(__dirname, 'index.js')];
+    const statSyncSpy = jest.spyOn(fs, 'statSync').mockReturnValue({} as any);
+    expect(isDocker()).toBeTruthy();
+    expect(statSyncSpy).toHaveBeenCalledTimes(1);
+    expect(statSyncSpy).toHaveBeenLastCalledWith('/.dockerenv');
+  });
+
+  it('inside a Docker container (cgroup test)', async () => {
+    delete require.cache[path.join(__dirname, 'index.js')];
+
+    const statSyncSpy = jest.spyOn(fs, 'statSync');
+    const readFileSyncSpy = jest.spyOn(fs, 'readFileSync');
+
+    statSyncSpy.mockImplementationOnce((path): any => {
+      if (path === '/.dockerenv') {
+        throw new Error("ENOENT, no such file or directory '/.dockerinit'");
+      }
+    });
+
+    readFileSyncSpy.mockImplementationOnce((path, options): any => {
+      if (path === '/proc/self/cgroup' && options === 'utf8') {
+        return 'xxx docker yyyy';
+      }
+    });
+
+    expect(isDocker()).toEqual(true);
+  });
+
+  it('not inside a Docker container', async () => {
+    const statSyncSpy = jest.spyOn(fs, 'statSync');
+    const readFileSync = jest.spyOn(fs, 'readFileSync');
+
+    statSyncSpy.mockImplementationOnce((path): any => {
+      if (path === '/.dockerenv') {
+        throw new Error("ENOENT, no such file or directory '/.dockerinit'");
+      }
+    });
+
+    readFileSync.mockImplementationOnce((): any => {
+      throw new Error("ENOENT, no such file or directory '/.dockerinit'");
+    });
+
+    expect(isDocker()).toEqual(false);
+  });
+});