DP-1.14: fix potential nil pointer dereference errors

[karthikeya-remilla]

In instances where the telemetry values are not received, code still goes on to check related data causing panic and test abortion. This diff plans to handle errors gracefully.

qos_basic_test.go:445: TransmitPkts count for queue "TenGigE0/0/0/0/2" on interface "AF3" not available within 1m0s
   --- FAIL: TestBasicConfigWithTraffic/Non-oversubscription_80_percent_of_linerate_traffic (69.51s)
panic: runtime error: invalid memory address or nil pointer dereference [recovered]
   panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x2 addr=0x0 pc=0x10a797fb4]

goroutine 12 [running]:
testing.tRunner.func1.2({0x10c028260, 0x117fe7980})
   /Users/karremil/go/pkg/mod/golang.org/toolchain@v0.0.1-go1.24.7.darwin-arm64/src/testing/testing.go:1734 +0x1ac
testing.tRunner.func1()
   /Users/karremil/go/pkg/mod/golang.org/toolchain@v0.0.1-go1.24.7.darwin-arm64/src/testing/testing.go:1737 +0x334
panic({0x10c028260?, 0x117fe7980?})
   /Users/karremil/go/pkg/mod/golang.org/toolchain@v0.0.1-go1.24.7.darwin-arm64/src/runtime/panic.go:792 +0x124
github.com/openconfig/ygnmi/ygnmi.(*Value[...]).Val(...)
   /Users/karremil/go/pkg/mod/github.com/openconfig/ygnmi@v0.14.0/ygnmi/ygnmi.go:126
github.com/openconfig/featureprofiles/feature/qos/otg_tests/qos_basic_test_test.TestBasicConfigWithTraffic.func1(0x14000503c00)
   /Users/karremil/GolandProjects/b4firex/featureprofiles/feature/qos/otg_tests/qos_basic_test/qos_basic_test.go:447 +0xa94
testing.tRunner(0x14000503c00, 0x14007e84060)
   /Users/karremil/go/pkg/mod/golang.org/toolchain@v0.0.1-go1.24.7.darwin-arm64/src/testing/testing.go:1792 +0xe4
created by testing.(*T).Run in goroutine 72
   /Users/karremil/go/pkg/mod/golang.org/toolchain@v0.0.1-go1.24.7.darwin-arm64/src/testing/testing.go:1851 +0x374

[gemini-code-assist]

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request addresses a stability issue in the QoS basic test suite where missing telemetry data caused nil pointer dereference panics. By implementing proper validation checks before accessing the returned values, the tests now handle missing data gracefully without aborting execution.

Highlights

• Error Handling: Added nil checks for telemetry values returned by gnmi.Watch to prevent runtime panics when data is missing.
• Control Flow: Updated logic to only attempt to access telemetry values if the watch operation is successful and the result is non-nil.

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[OpenConfigBot]

Pull Request Functional Test Report for #5363 / d86deda

Virtual Devices

Device	Test	Test Documentation	Job	Raw Log
Arista cEOS		DP-1.14: QoS basic test
Cisco 8000E		DP-1.14: QoS basic test
Cisco XRd		DP-1.14: QoS basic test
Juniper ncPTX		DP-1.14: QoS basic test
Nokia SR Linux		DP-1.14: QoS basic test
Openconfig Lemming		DP-1.14: QoS basic test

Hardware Devices

Device	Test	Test Documentation	Raw Log
Arista 7808		DP-1.14: QoS basic test
Cisco 8808		DP-1.14: QoS basic test
Juniper PTX10008		DP-1.14: QoS basic test
Nokia 7250 IXR-10e		DP-1.14: QoS basic test

Help

[gemini-code-assist]

Code Review

This pull request updates the QoS basic test by adding null checks for counter values and correcting the argument order in error messages. The review feedback suggests using t.Fatalf instead of t.Errorf for these critical counter retrievals to ensure the test fails fast if baseline data is unavailable. Furthermore, the reviewer noted that the explicit count == nil checks are redundant because the ok return value from Await(t) already guarantees the presence of a non-nil value.

[karthikeya-remilla]

@AmrNJ please help in getting this merged by requesting internal reviews.