observability-testing

To test structured logging in TypeScript, you use a mock logger to capture entries and assertion helpers like assertLogEntry to verify exact output and log levels in unit and integration tests.

Yes, you can enforce a log level policy using a LOG_LEVEL_POLICY reference and a classifyLogLevel helper, ensuring consistent logging practices and preventing unexpected log levels across your JavaScript or TypeScript project.

You can assert that no warnings or errors were logged by using the assertNoLogsAbove helper, which checks the captured mock logger entries against your specified log level policy to fail the test if higher severity logs are present.

Yes, this observability testing approach works with existing JavaScript and TypeScript test suites by integrating a strict structured-logger interface and mock logger, requiring only a TypeScript runtime for compatibility.

The best way to verify error logs in integration tests is using a mock logger to capture entries and the assertErrorLogged helper, which validates that the expected error level entries were generated during code execution.