[Engineering task] Fix tests

[gladjohn]

Task type

Test

Description

extraExpectedHeaders is assigned to TestConstants.s_extraHttpHeader (a static Dictionary) and then mutated via Add(...). This makes the shared static headers stateful across tests and can create order-dependent/flaky behavior. Create a per-test copy of the dictionary before adding the CCS header, and pass that same per-test instance to both the mock handler setup and WithExtraHttpHeaders.

Solution

No response