Faster datascience tests with fake timers (microsoft#9272)

DonJayamanne · web-flow · commit 42bd4f295e48 · 2019-12-23T15:21:02.000-08:00
Faster tests with fake timers.
Speed up tests that have Sleep(n)

Speed up of tests from 10s to 54ms with two easy lines (install &amp; wait)
diff --git a/.nvmrc b/.nvmrc
@@ -1 +1 @@
-v10.5.0
+v10.11.0
diff --git a/package-lock.json b/package-lock.json
diff --git a/package.json b/package.json
@@ -2841,7 +2841,7 @@
         "@types/request": "^2.47.0",
         "@types/semver": "^5.5.0",
         "@types/shortid": "^0.0.29",
-        "@types/sinon": "^7.0.13",
+        "@types/sinon": "^7.5.1",
         "@types/stack-trace": "0.0.29",
         "@types/temp": "^0.8.32",
         "@types/tmp": "0.0.33",
@@ -2906,6 +2906,7 @@
         "less": "^3.9.0",
         "less-loader": "^5.0.0",
         "loader-utils": "^1.1.0",
+        "lolex": "^5.1.2",
         "mocha": "^6.1.4",
         "mocha-junit-reporter": "^1.17.0",
         "mocha-multi-reporters": "^1.1.7",
@@ -2930,7 +2931,7 @@
         "sass-loader": "^7.1.0",
         "serialize-javascript": "^2.1.2",
         "shortid": "^2.2.8",
-        "sinon": "^7.3.2",
+        "sinon": "^8.0.1",
         "source-map-support": "^0.5.12",
         "style-loader": "^0.23.1",
         "styled-jsx": "^3.1.0",
diff --git a/src/test/common.ts b/src/test/common.ts
@@ -445,3 +445,80 @@ export async function openFile(file: string): Promise<TextDocument> {
     assert(vscode.window.activeTextEditor, 'No active editor');
     return textDocument;
 }
+
+/**
+ * Fakes for timers in nodejs when testing, using `lolex`.
+ * An alternative to `sinon.useFakeTimers` (which in turn uses `lolex`, but doesn't expose the `async` methods).
+ * Use this class when you have tests with `setTimeout` and which to avoid them for faster tests.
+ *
+ * For further information please refer:
+ * - https://www.npmjs.com/package/lolex
+ * - https://sinonjs.org/releases/v1.17.6/fake-timers/
+ *
+ * @class FakeClock
+ */
+export class FakeClock {
+    // tslint:disable-next-line:no-any
+    private clock?: any;
+    /**
+     * Creates an instance of FakeClock.
+     * @param {number} [advacenTimeMs=10_000] Default `timeout` value. Defaults to 10s. Assuming we do not have anything bigger.
+     * @memberof FakeClock
+     */
+    constructor(private readonly advacenTimeMs: number = 10_000) {}
+    public install() {
+        // tslint:disable-next-line:no-require-imports
+        const lolex = require('lolex');
+        this.clock = lolex.install();
+    }
+    public uninstall() {
+        this.clock?.uninstall();
+    }
+    /**
+     * Wait for timers to kick in, and then wait for all of them to complete.
+     *
+     * @returns {Promise<void>}
+     * @memberof FakeClock
+     */
+    public async wait(): Promise<void> {
+        await this.waitForTimersToStart();
+        await this.waitForTimersToFinish();
+    }
+
+    /**
+     * Wait for timers to start.
+     *
+     * @returns {Promise<void>}
+     * @memberof FakeClock
+     */
+    private async waitForTimersToStart(): Promise<void> {
+        if (!this.clock){
+            throw new Error('Fake clock not installed');
+        }
+        while (this.clock.countTimers() === 0) {
+            // Relinquish control to event loop, so other timer code will run.
+            // We want to wait for `setTimeout` to kick in.
+            await new Promise(resolve => process.nextTick(resolve));
+        }
+    }
+    /**
+     * Wait for timers to finish.
+     *
+     * @returns {Promise<void>}
+     * @memberof FakeClock
+     */
+    private async waitForTimersToFinish(): Promise<void> {
+        if (!this.clock){
+            throw new Error('Fake clock not installed');
+        }
+        while (this.clock.countTimers()) {
+            // Advance clock by 10s (can be anything to ensure the next scheduled block of code executes).
+            // Assuming we do not have timers > 10s
+            // This will ensure any such such as `setTimeout(..., 10)` will get executed.
+            this.clock.tick(this.advacenTimeMs);
+
+            // Wait for the timer code to run to completion (incase they are promises).
+            await this.clock.runAllAsync();
+        }
+    }
+}
diff --git a/src/test/datascience/jupyter/kernels/kernelService.unit.test.ts b/src/test/datascience/jupyter/kernels/kernelService.unit.test.ts
@@ -30,6 +30,7 @@ import { EnvironmentActivationService } from '../../../../client/interpreter/act
 import { IEnvironmentActivationService } from '../../../../client/interpreter/activation/types';
 import { IInterpreterService, InterpreterType, PythonInterpreter } from '../../../../client/interpreter/contracts';
 import { InterpreterService } from '../../../../client/interpreter/interpreterService';
+import { FakeClock } from '../../../common';
 
 // tslint:disable-next-line: max-func-body-length
 suite('Data Science - KernelService', () => {
@@ -222,6 +223,7 @@ suite('Data Science - KernelService', () => {
     // tslint:disable-next-line: max-func-body-length
     suite('Registering Interpreters as Kernels', () => {
         let findMatchingKernelSpecStub: sinon.SinonStub<[PythonInterpreter, IJupyterSessionManager?, (CancellationToken | undefined)?], Promise<IJupyterKernelSpec | undefined>>;
+        let fakeTimer: FakeClock;
         const interpreter: PythonInterpreter = {
             architecture: Architecture.Unknown,
             path: path.join('interpreter', 'python'),
@@ -246,9 +248,12 @@ suite('Data Science - KernelService', () => {
 
         setup(() => {
             findMatchingKernelSpecStub = sinon.stub(KernelService.prototype, 'findMatchingKernelSpec');
+            fakeTimer = new FakeClock();
             initialize();
         });
 
+        teardown(() => fakeTimer.uninstall());
+
         test('Fail if interpreter does not have a display name', async () => {
             const invalidInterpreter: PythonInterpreter = {
                 architecture: Architecture.Unknown,
@@ -266,32 +271,36 @@ suite('Data Science - KernelService', () => {
             when(execService.execModule('ipykernel', anything(), anything())).thenResolve({ stdout: '' });
             when(installer.isInstalled(Product.ipykernel, interpreter)).thenResolve(true);
             findMatchingKernelSpecStub.resolves(undefined);
+            fakeTimer.install();
 
             const promise = kernelService.registerKernel(interpreter);
 
+            await fakeTimer.wait();
             await assert.isRejected(promise);
             verify(execService.execModule('ipykernel', anything(), anything())).once();
             const installArgs = capture(execService.execModule).first()[1] as string[];
             const kernelName = installArgs[3];
             assert.deepEqual(installArgs, ['install', '--user', '--name', kernelName, '--display-name', interpreter.displayName]);
             await assert.isRejected(promise, `Kernel not created with the name ${kernelName}, display_name ${interpreter.displayName}. Output is `);
-        }).timeout(10_000);
+        });
         test('If ipykernel is not installed, then prompt to install ipykernel', async () => {
             when(execService.execModule('ipykernel', anything(), anything())).thenResolve({ stdout: '' });
             when(installer.isInstalled(Product.ipykernel, interpreter)).thenResolve(false);
             when(installer.promptToInstall(anything(), anything(), anything())).thenResolve(InstallerResponse.Installed);
             findMatchingKernelSpecStub.resolves(undefined);
+            fakeTimer.install();
 
             const promise = kernelService.registerKernel(interpreter);
 
+            await fakeTimer.wait();
             await assert.isRejected(promise);
             verify(execService.execModule('ipykernel', anything(), anything())).once();
             const installArgs = capture(execService.execModule).first()[1] as string[];
             const kernelName = installArgs[3];
             assert.deepEqual(installArgs, ['install', '--user', '--name', kernelName, '--display-name', interpreter.displayName]);
             await assert.isRejected(promise, `Kernel not created with the name ${kernelName}, display_name ${interpreter.displayName}. Output is `);
             verify(installer.promptToInstall(anything(), anything(), anything())).once();
-        }).timeout(10_000);
+        });
         test('If ipykernel is not installed, and ipykerne installation is canclled, then do not reigster kernel', async () => {
             when(execService.execModule('ipykernel', anything(), anything())).thenResolve({ stdout: '' });
             when(installer.isInstalled(Product.ipykernel, interpreter)).thenResolve(false);
@@ -303,7 +312,7 @@ suite('Data Science - KernelService', () => {
             assert.isUndefined(kernel);
             verify(execService.execModule('ipykernel', anything(), anything())).never();
             verify(installer.promptToInstall(anything(), anything(), anything())).once();
-        }).timeout(10_000);
+        });
         test('Fail if installed kernel is not an instance of JupyterKernelSpec', async () => {
             when(execService.execModule('ipykernel', anything(), anything())).thenResolve({ stdout: '' });
             when(installer.isInstalled(Product.ipykernel, interpreter)).thenResolve(true);
