refactor: reduce dry4dotnet duplication

[marandaneto]

💡 Motivation and Context

Refactor duplicate code paths found by the dry4dotnet PoC (github.com/marandaneto/dry4dotnet) without changing the public API or behavior.

This reduces repeated implementation/test patterns in group identify helpers, no-op client methods, capture helpers, sample setup, fake HTTP response helpers, and several duplicate-heavy tests.

💚 How did you test it?

• dotnet build PostHog.sln --no-restore
• dotnet test PostHog.sln --no-build --no-restore
• dotnet test tests/UnitTests/UnitTests.csproj --framework net8.0 --no-restore --filter "FullyQualifiedName~SemanticVersionTests"
• dotnet test tests/UnitTests/UnitTests.csproj --framework net8.0 --no-restore --filter "FullyQualifiedName~TheIdentifyGroupAsyncMethod|FullyQualifiedName~TheCapturePageViewMethod|FullyQualifiedName~TheNoOpPostHogClient"
• dotnet test tests/UnitTests/UnitTests.csproj --framework net8.0 --no-build --no-restore --filter "FullyQualifiedName~SemanticVersionTests|FullyQualifiedName~LocalEvaluatorTests|FullyQualifiedName~FeatureFlagErrorTracking"
• Re-ran dry4dotnet PoC and reduced candidates from 284 to 126.

📝 Checklist

• I reviewed the submitted code.
• I added tests to verify the changes.
• I updated the docs if needed.
• No breaking change or entry added to the changelog.

If releasing new changes

• Ran pnpm changeset to generate a changeset file

[github-actions]

posthog-dotnet Compliance Report

Date: 2026-06-05 10:25:27 UTC
Duration: 610ms

⚠️ Some Tests Failed

2/16 tests passed, 14 failed

---

Feature_Flags Tests

⚠️ 2/16 tests passed, 14 failed

View Details

Test	Status	Duration
Request Payload.Request With Person Properties Device Id	❌	43ms
Request Payload.Flags Request Uses V2 Query Param	❌	22ms
Request Payload.Flags Request Hits Flags Path Not Decide	❌	5ms
Request Payload.Flags Request Omits Authorization Header	❌	5ms
Request Payload.Token In Flags Body Matches Init	❌	5ms
Request Payload.Groups Round Trip	❌	5ms
Request Payload.Groups Default To Empty Object	❌	5ms
Request Payload.Person Properties Distinct Id Auto Populated When Caller Omits It	❌	4ms
Request Payload.Disable Geoip False Propagates As Geoip Disable False	❌	12ms
Request Payload.Disable Geoip Omitted Defaults To False	❌	12ms
Request Payload.Flag Keys To Evaluate Contains Only Requested Key	❌	6ms
Request Lifecycle.No Flags Request On Init Alone	✅	4ms
Request Lifecycle.No Flags Request On Normal Capture	✅	186ms
Request Lifecycle.Two Flag Calls Produce Two Remote Requests	❌	7ms
Request Lifecycle.Mock Response Value Is Returned To Caller	❌	5ms
Side Effect Events.Get Feature Flag Captures Feature Flag Called Event	❌	5ms

Failures

request_payload.request_with_person_properties_device_id

404, message='Not Found', url='http://sdk-adapter:8080/get_feature_flag'

request_payload.flags_request_uses_v2_query_param

404, message='Not Found', url='http://sdk-adapter:8080/get_feature_flag'

request_payload.flags_request_hits_flags_path_not_decide

404, message='Not Found', url='http://sdk-adapter:8080/get_feature_flag'

request_payload.flags_request_omits_authorization_header

404, message='Not Found', url='http://sdk-adapter:8080/get_feature_flag'

request_payload.token_in_flags_body_matches_init

404, message='Not Found', url='http://sdk-adapter:8080/get_feature_flag'

request_payload.groups_round_trip

404, message='Not Found', url='http://sdk-adapter:8080/get_feature_flag'

request_payload.groups_default_to_empty_object

404, message='Not Found', url='http://sdk-adapter:8080/get_feature_flag'

request_payload.person_properties_distinct_id_auto_populated_when_caller_omits_it

404, message='Not Found', url='http://sdk-adapter:8080/get_feature_flag'

request_payload.disable_geoip_false_propagates_as_geoip_disable_false

404, message='Not Found', url='http://sdk-adapter:8080/get_feature_flag'

request_payload.disable_geoip_omitted_defaults_to_false

404, message='Not Found', url='http://sdk-adapter:8080/get_feature_flag'

request_payload.flag_keys_to_evaluate_contains_only_requested_key

404, message='Not Found', url='http://sdk-adapter:8080/get_feature_flag'

request_lifecycle.two_flag_calls_produce_two_remote_requests

404, message='Not Found', url='http://sdk-adapter:8080/get_feature_flag'

request_lifecycle.mock_response_value_is_returned_to_caller

404, message='Not Found', url='http://sdk-adapter:8080/get_feature_flag'

side_effect_events.get_feature_flag_captures_feature_flag_called_event

404, message='Not Found', url='http://sdk-adapter:8080/get_feature_flag'

[greptile-apps]

Comments Outside Diff (2)

1. tests/UnitTests/Library/SemanticVersionTests.cs, line 1068 (link)

   Literal tab characters reduce readability

   The escape sequence "\t1.2.3\t" was replaced with a string containing literal tab characters. Both are functionally identical, but the literal form is nearly invisible in most editors and code-review tools — it looks like ordinary indentation rather than whitespace that is part of the test value. The escaped form was far more self-documenting.

   Prompt To Fix With AI

   This is a comment left during a code review.
   Path: tests/UnitTests/Library/SemanticVersionTests.cs
   Line: 1068
   
   Comment:
   **Literal tab characters reduce readability**
   
   The escape sequence `"\t1.2.3\t"` was replaced with a string containing literal tab characters. Both are functionally identical, but the literal form is nearly invisible in most editors and code-review tools — it looks like ordinary indentation rather than whitespace that is part of the test value. The escaped form was far more self-documenting.
   
   How can I resolve this? If you propose a fix, please make it concise.

   Note: If this suggestion doesn't match your team's coding style, reply to this and let me know. I'll remember it for next time!

2. tests/UnitTests/Library/SemanticVersionTests.cs, line 1554-1560 (link)

   Silent catch-all in switch could mask a test-data typo

   The _ => arm silently evaluates >= for any operatorName value that is not <, <=, or >. If a future test case accidentally uses "=>" (reversed) or ">= " (trailing space), the switch executes >= without warning, producing a passing test that exercises the wrong operator. Consider throwing in the _ arm so any mismatched string fails loudly. The same silent-fallback pattern applies to the kind == "tilde" ? ... : ... dispatch in CalculatesCorrectBounds and BoundsMatchCorrectly.

   Prompt To Fix With AI

   This is a comment left during a code review.
   Path: tests/UnitTests/Library/SemanticVersionTests.cs
   Line: 1554-1560
   
   Comment:
   **Silent catch-all in switch could mask a test-data typo**
   
   The `_ =>` arm silently evaluates `>=` for any `operatorName` value that is not `<`, `<=`, or `>`. If a future test case accidentally uses `"=>"` (reversed) or `">= "` (trailing space), the switch executes `>=` without warning, producing a passing test that exercises the wrong operator. Consider throwing in the `_` arm so any mismatched string fails loudly. The same silent-fallback pattern applies to the `kind == "tilde" ? ... : ...` dispatch in `CalculatesCorrectBounds` and `BoundsMatchCorrectly`.
   
   How can I resolve this? If you propose a fix, please make it concise.

Prompt To Fix All With AI

Fix the following 2 code review issues. Work through them one at a time, proposing concise fixes.

---

### Issue 1 of 2
tests/UnitTests/Library/SemanticVersionTests.cs:1068
**Literal tab characters reduce readability**

The escape sequence `"\t1.2.3\t"` was replaced with a string containing literal tab characters. Both are functionally identical, but the literal form is nearly invisible in most editors and code-review tools — it looks like ordinary indentation rather than whitespace that is part of the test value. The escaped form was far more self-documenting.

### Issue 2 of 2
tests/UnitTests/Library/SemanticVersionTests.cs:1554-1560
**Silent catch-all in switch could mask a test-data typo**

The `_ =>` arm silently evaluates `>=` for any `operatorName` value that is not `<`, `<=`, or `>`. If a future test case accidentally uses `"=>"` (reversed) or `">= "` (trailing space), the switch executes `>=` without warning, producing a passing test that exercises the wrong operator. Consider throwing in the `_` arm so any mismatched string fails loudly. The same silent-fallback pattern applies to the `kind == "tilde" ? ... : ...` dispatch in `CalculatesCorrectBounds` and `BoundsMatchCorrectly`.

_{Reviews (1): Last reviewed commit: "refactor: reduce dry4dotnet duplication" | Re-trigger Greptile}

[marandaneto]

Addressed Greptile feedback in 0c6c389: restored escaped tab test data for readability and made the test dispatch fail loudly for unknown range/operator strings. Verified with dotnet test tests/UnitTests/UnitTests.csproj --framework net8.0 --no-restore --filter "FullyQualifiedName~SemanticVersionTests".