"Cannot read property 'tests' of null" when using client scripts

[Aaronius]

What is your Test Scenario?

My test scenario can be as simple as this:

fixture`Getting Started`.page`http://devexpress.github.io/testcafe/example`;

test("My first test", async t => {
  // Test code
});

But this issue isn't so much about my test scenario as it is configuring the testcafe runner with clientScripts. Here's my setup:

await testcafe
    .createLiveModeRunner()
    .clientScripts("preventSpecificErrorsFromFailingTests.js")
    .src(testsDir)
    .browsers("chrome")
    .run();

What is the Current behavior?

I receive the following error in the console:

TypeError: Cannot read property 'tests' of null
    at LiveModeRunner._finishPreviousTestRuns (/Users/aahardy/dev/reactor-extension-alloy/node_modules/testcafe/src/live/test-runner.js:151:38)
    at LiveModeRunner.runTests (/Users/aahardy/dev/reactor-extension-alloy/node_modules/testcafe/src/live/test-runner.js:36:21)
    at /Users/aahardy/dev/reactor-extension-alloy/node_modules/testcafe/src/live/test-runner.js:113:30
Error: Cannot load a client script from preventSpecificErrorsFromFailingTests.js.
    at ClientScript._loadFromPath (/Users/aahardy/dev/reactor-extension-alloy/node_modules/testcafe/src/custom-client-scripts/client-script.ts:64:19)
    at ClientScript.load (/Users/aahardy/dev/reactor-extension-alloy/node_modules/testcafe/src/custom-client-scripts/client-script.ts:91:13)
    at async Promise.all (index 0)
    at Object.default_1 [as default] (/Users/aahardy/dev/reactor-extension-alloy/node_modules/testcafe/src/custom-client-scripts/load.ts:11:5)
    at LiveModeBootstrapper.createRunnableConfiguration (/Users/aahardy/dev/reactor-extension-alloy/node_modules/testcafe/src/runner/bootstrapper.ts:419:37)

What is the Expected behavior?

A successful test run. Note that if I remove the .clientScripts("preventSpecificErrorsFromFailingTests.js") line, the test run completes just fine. Currently my preventSpecificErrorsFromFailingTests.js file contains no content, but it doesn't really matter what I put in that file.

What is your web application and your TestCafe test code?

Your website URL (or attach your complete example):

Your complete test code (or attach your test files):

 fixture`Getting Started`.page`http://devexpress.github.io/testcafe/example`;

test("My first test", async t => {
  // Test code
});

Your complete configuration file (if any):

#!/usr/bin/env node
const path = require("path");
const createTestCafe = require("testcafe");
const testsDir = path.join(__dirname, "../test/sample");

(async () => {
  const testcafe = await createTestCafe("localhost", 1337, 1338);
  const failedCount = await testcafe
    .createLiveModeRunner()
    .clientScripts("preventSpecificErrorsFromFailingTests.js")
    .src(testsDir)
    .browsers("chrome")
    .run();
  testcafe.close();
  process.exit(failedCount ? 1 : 0);
})();

Your complete test report:

N/A

Screenshots:

N/A

Steps to Reproduce:

1. Clone https://github.com/Aaronius/testcafe-bugs
2. Checkout the client-scripts branch
3. Run npm install
4. Run npm test

Your Environment details:

• testcafe version: 1.14.2
• node.js version: 14.16.1
• command-line arguments: None, just using the library as described.
• browser name and version: Chrome 91
• platform and version: Mac Catalina
• other:

[miherlosev]

Hi @Aaronius

Thank you for the shared example. I've reproduced the issue.