Docker execution in Cypress - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Cypress Docker container test run output

You run a Cypress test inside a Docker container using the command:

docker run -it -v $PWD:/e2e -w /e2e cypress/included:12.0.0

The test suite contains 3 passing tests and 1 failing test. What will the Docker container output indicate after the run?

A The container exits with code 0 and shows '4 tests passed' in the logs.

B The container exits with a non-zero code but shows 'All tests passed' in the logs.

C The container exits with code 0 but shows '1 test failed' in the logs.

D The container exits with a non-zero code and shows '3 tests passed, 1 test failed' in the logs.

💡 Hint

Remember that Cypress Docker images exit with a non-zero code if any test fails.

When Cypress tests run inside the official Docker container, if any test fails, the container exits with a non-zero code. The logs will show the number of passing and failing tests accurately.

❓ assertion

intermediate

Correct assertion to verify test run success in Cypress Docker

You want to write a script that runs Cypress tests inside Docker and asserts the container exited successfully (all tests passed). Which assertion correctly checks the Docker container exit code in a Node.js script?

Cypress

const { exec } = require('child_process');
exec('docker run -it -v $PWD:/e2e -w /e2e cypress/included:12.0.0', (error, stdout, stderr) => {
  // Which assertion below correctly verifies success?
});

A assert.strictEqual(error, null);

B assert.strictEqual(error.code, 0);

C assert.strictEqual(error, 0);

D assert.strictEqual(error, undefined);

💡 Hint

In Node.js exec callback, error is null if the command succeeds.

The exec callback's error argument is null when the command exits with code 0 (success). Checking error.code or error directly is incorrect because error is either null or an Error object.

🔧 Debug

advanced

Debugging Cypress tests failing silently in Docker

You run Cypress tests inside Docker, but the container exits with code 0 and the logs show no test results. What is the most likely cause?

A The Docker container ran out of memory and crashed silently.

B The test files are not mounted correctly into the container volume.

C The Cypress version in Docker is incompatible with the test code.

D The Docker network settings prevent Cypress from running tests.

💡 Hint

Check if your test files are accessible inside the container.

If the test files are not mounted or mapped correctly into the Docker container, Cypress will run but find no tests, exiting with code 0 and no results.

❓ framework

advanced

Best practice for running Cypress tests in CI with Docker

Which approach is best to run Cypress tests inside Docker in a Continuous Integration (CI) pipeline to ensure consistent test results?

A Use the official Cypress Docker image with a fixed version tag and mount the test code as a volume.

B Build a custom Docker image with the latest Cypress version installed dynamically at runtime.

C Run Cypress tests directly on the host machine without Docker for faster execution.

D Use the official Cypress Docker image without specifying a version tag to always get the latest.

💡 Hint

Consistency and reproducibility are key in CI environments.

Using the official Cypress Docker image with a fixed version tag ensures tests run in a consistent environment. Mounting the test code as a volume allows easy updates without rebuilding the image.

🧠 Conceptual

expert

Understanding Cypress Docker container exit codes

What does a non-zero exit code from a Cypress Docker container indicate after test execution?

A The tests were skipped because no test files were found.

B All tests passed successfully without any errors.

C At least one test failed or an error occurred during test execution.

D The Docker container failed to start due to configuration issues.

💡 Hint

Non-zero exit codes usually signal failure or errors.

Cypress Docker containers exit with code 0 only if all tests pass. A non-zero exit code means one or more tests failed or there was an error during execution.