MQTT test refactor PR (#818) crashes WebSocket tests in environments without IoT credentials

[kaukabrizvi]

Describe the bug

s2n-tls is the TLS/SSL implementation used by aws-crt-cpp. As part of s2n-tls CI, the s2nUnitCRT job in the s2nGeneralBatch job builds aws-crt-cpp from latest main, substitutes in the current s2n-tls source, and runs the full aws-crt-cpp test suite. This validates that s2n-tls changes don't break the CRT integration. The job runs without IoT credentials or AWS config files since it's purely a build/unit-test environment.

After the merge of #818 ("Mqtt test refactor"), 5 MQTT5 WebSocket tests in s2n-tls crash with a fatal assertion (Signal received: 0) instead of gracefully skipping in CI environments that lack IoT credentials:

This breaks downstream CI for any project that builds and tests aws-crt-cpp without IoT credentials (e.g., s2n-tls's s2nUnitCRT job). For immediate resolution, we can pin to the commit prior to the breaking PR. Once this issue is resolved, we can return to testing from latest.

Regression Issue

• Select this option if this issue appears to be a regression.

Expected Behavior

The WebSocket MQTT5 tests (Mqtt5WSConnectionWithMutualTLS, Mqtt5WSConnectionWithHttpProxy, Mqtt5WSConnectionFull, Mqtt5to3AdapterWSConnectionMinimalThroughMqtt3, Mqtt5to3AdapterWSConnectionMinimalThroughMqtt5) should gracefully skip when run in CI environments without IoT credentials, as they did prior to PR #818.

Current Behavior

After PR #818 ("Mqtt test refactor"), these 5 tests crash with Signal received: 0, errno: 0 and a stack trace instead of skipping. The refactored createTestContext function's MQTT5CONNECT_WS_IOT_CORE case unconditionally calls CredentialsProvider::CreateCredentialsProviderChainDefault() and passes the result into Aws::Iot::WebsocketConfig without validation. In environments without AWS credentials, the default chain falls through to the ECS provider and the resulting state triggers a fatal assertion during client construction. The old per-test code either required certs (causing an early skip) or had explicit ASSERT_TRUE(provider) checks that are now missing from the shared path.

Reproduction Steps

Build and run the aws-crt-cpp tests on a machine without IoT credentials or AWS config files. All 5 tests should crash with Signal received: 0 as observed in https://us-west-2.codebuild.aws.amazon.com/project/eyJlbmNyeXB0ZWREYXRhIjoidUpNb2QzNjZzQ3lrWm1UQ2xzdFZMN1ZGYWE5dVlSQ1ZKd1BnZzZ6aXN1dlZXTmFuZWdvNnR0SitPaFlIcUdjaDZ6RU9KemY2Mi9ybXVBajF0RXo4NmZ1Rnl4dkZrT241UUY4MTVQMkRuNTQ9IiwiaXZQYXJhbWV0ZXJTcGVjIjoiemFRUDgvZUMreVhER0RKaiIsIm1hdGVyaWFsU2V0U2VyaWFsIjoxfQ%3D%3D/build/58f37502-7178-47d6-bb62-64b2261f1e4d. On commit 7cb4eaa (one before the refactor), the same tests skip cleanly as observed in https://us-west-2.codebuild.aws.amazon.com/project/eyJlbmNyeXB0ZWREYXRhIjoidUpNb2QzNjZzQ3lrWm1UQ2xzdFZMN1ZGYWE5dVlSQ1ZKd1BnZzZ6aXN1dlZXTmFuZWdvNnR0SitPaFlIcUdjaDZ6RU9KemY2Mi9ybXVBajF0RXo4NmZ1Rnl4dkZrT241UUY4MTVQMkRuNTQ9IiwiaXZQYXJhbWV0ZXJTcGVjIjoiemFRUDgvZUMreVhER0RKaiIsIm1hdGVyaWFsU2V0U2VyaWFsIjoxfQ%3D%3D/build/b4cbe105-20b7-4164-b49a-c2380eb729d8

Possible Solution

Either validate the credentials provider in the MQTT5CONNECT_WS_IOT_CORE case of createTestContext and skip if it's null/invalid, or gate the MQTT5CONNECT_WS_IOT_CORE env var check on an additional credential-availability check so the test skips properly.

Additional Information/Context

No response

aws-crt-cpp version used

main at commit fbb9615 (includes PR #818, "Mqtt test refactor"). Last working commit: 7cb4eaa.

Compiler and version used

GCC 13

Operating System and version

Ubuntu 24 (x86_64 Linux)

[bretambrose]

Thank you for the report.

There's a trivial fix to skip the tests, but I think the larger issue is that default provider chain construction should never crash. Looking into that further.

Is there any way for you run the s2n build with debug symbols?

FWIW, your build environment does have an ECS credentials environment, but nothing else.

[bretambrose]

Looks like a false alarm on the provider construction crash. Adding the test skip.

[bretambrose]

Should be addressed by #845