test(openfeature): add STATIC and SPLIT reason assertions

[leoromanovsky]

Motivation

The Ruby evaluation_engine_spec.rb tests assert ERROR and MATCH reason paths, but do not verify STATIC or SPLIT reason values. The native evaluator (Rust FFI via libdatadog) already returns correct reason values, but without test assertions, regressions in the reason contract would go undetected.

This is part of a cross-SDK effort to ensure all OpenFeature reason values are covered by tests (see dd-trace-cross-repo planning).

Changes

• Added STATIC reason test context: verifies the override path (no rules, 1 split, no shards) returns reason: 'STATIC'
• Added SPLIT reason test context: verifies shard-based assignment returns reason: 'SPLIT'
• Added MATCH reason assertion to the existing resolution details context (previously only asserted value, not reason)
• All existing ERROR reason tests remain unchanged

Decisions

• Mock-based approach: These tests stub NativeEvaluator#get_assignment to return ResolutionDetails with specific reason values, matching the existing test pattern. This verifies the engine correctly propagates reason values from the evaluator.
• No lib/ changes: The native evaluator already computes correct reasons; only test coverage was missing.

[github-actions]

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^{Visited at: 2026-03-26 01:40:24 UTC}

[datadog-datadog-prod-us1-2]

⚠️ Tests

✨ Fix all issues with BitsAI or with Cursor

⚠️ Warnings

❄️ 103 New flaky tests detected

OpenFeature evaluation fixtures test-case-kill-switch-flag.json case 0/alice from rspec     (Fix with Cursor)

wrong number of arguments (given 1, expected 0)

Failure/Error: let(:configuration) { Datadog::Core::FeatureFlags::Configuration.new(config_json) }

ArgumentError:
  wrong number of arguments (given 1, expected 0)
./spec/datadog/open_feature/fixture_spec.rb:9:in 'BasicObject#initialize'
./spec/datadog/open_feature/fixture_spec.rb:9:in 'Class#new'
./spec/datadog/open_feature/fixture_spec.rb:9:in 'block (2 levels) in <top (required)>'
./spec/datadog/open_feature/fixture_spec.rb:53:in 'block (5 levels) in <top (required)>'
...

OpenFeature evaluation fixtures test-case-kill-switch-flag.json case 1/bob from rspec     (Fix with Cursor)

wrong number of arguments (given 1, expected 0)

Failure/Error: let(:configuration) { Datadog::Core::FeatureFlags::Configuration.new(config_json) }

ArgumentError:
  wrong number of arguments (given 1, expected 0)
./spec/datadog/open_feature/fixture_spec.rb:9:in 'BasicObject#initialize'
./spec/datadog/open_feature/fixture_spec.rb:9:in 'Class#new'
./spec/datadog/open_feature/fixture_spec.rb:9:in 'block (2 levels) in <top (required)>'
./spec/datadog/open_feature/fixture_spec.rb:53:in 'block (5 levels) in <top (required)>'
...

OpenFeature evaluation fixtures test-case-kill-switch-flag.json case 10/6 from rspec     (Fix with Cursor)

wrong number of arguments (given 1, expected 0)

Failure/Error: let(:configuration) { Datadog::Core::FeatureFlags::Configuration.new(config_json) }

ArgumentError:
  wrong number of arguments (given 1, expected 0)
./spec/datadog/open_feature/fixture_spec.rb:9:in 'BasicObject#initialize'
./spec/datadog/open_feature/fixture_spec.rb:9:in 'Class#new'
./spec/datadog/open_feature/fixture_spec.rb:9:in 'block (2 levels) in <top (required)>'
./spec/datadog/open_feature/fixture_spec.rb:53:in 'block (5 levels) in <top (required)>'
...

View all

🧪 1 Test failed

gem release process datadog.gemspec files includes all important files from rspec     (Fix with Cursor)

Failure/Error:
  expect(gemspec.files)
    .to match_array(
      \`git ls-files -z\`
        .split("\x0")
        .reject { |f| f.match(directories_excluded) }
        .reject { |f| f.match(single_files_excluded) }
    )

  expected collection contained:  [".gitmodules", "CHANGELOG.md", "LICENSE", "LICENSE-3rdparty.csv", "LICENSE.Apache", "LICENSE.BSD3", ...ls.rb", "lib/datadog/tracing/workers.rb", "lib/datadog/tracing/writer.rb", "lib/datadog/version.rb"]
...

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