[Issue #2] Add unit tests for ConsistentHashRing #30

HugoNijhuis · 2026-01-09T15:52:49Z

HugoNijhuis commented

2026-01-09 15:52:49 +00:00

Summary

Add comprehensive unit tests for ConsistentHashRing with 100% coverage on hashring.go
Test all public methods: NewConsistentHashRing, AddNode, RemoveNode, GetNode, GetNodes, IsEmpty
Verify key distribution is balanced across nodes (< 25% deviation)
Test minimal key movement when adding nodes (consistent hashing property)
Verify virtual nodes improve distribution (coefficient of variation < 15%)
Test edge cases: empty ring, single node, 100+ nodes, various node ID formats
Include benchmarks for performance testing

Closes #2

Test plan

All 24 tests pass
100% coverage on cluster/hashring.go
Tests cover all acceptance criteria:
- AddNode correctly updates ring
- RemoveNode correctly updates ring
- GetNode returns consistent results for same key
- Key distribution is reasonably balanced
- Ring behavior with single node
- Ring behavior with many nodes (100+)
- Virtual nodes improve distribution

🤖 Generated with Claude Code

## Summary - Add comprehensive unit tests for `ConsistentHashRing` with 100% coverage on hashring.go - Test all public methods: `NewConsistentHashRing`, `AddNode`, `RemoveNode`, `GetNode`, `GetNodes`, `IsEmpty` - Verify key distribution is balanced across nodes (< 25% deviation) - Test minimal key movement when adding nodes (consistent hashing property) - Verify virtual nodes improve distribution (coefficient of variation < 15%) - Test edge cases: empty ring, single node, 100+ nodes, various node ID formats - Include benchmarks for performance testing Closes #2 ## Test plan - [x] All 24 tests pass - [x] 100% coverage on cluster/hashring.go - [x] Tests cover all acceptance criteria: - [x] AddNode correctly updates ring - [x] RemoveNode correctly updates ring - [x] GetNode returns consistent results for same key - [x] Key distribution is reasonably balanced - [x] Ring behavior with single node - [x] Ring behavior with many nodes (100+) - [x] Virtual nodes improve distribution 🤖 Generated with [Claude Code](https://claude.com/claude-code)

HugoNijhuis added 1 commit 2026-01-09 15:52:49 +00:00

Add comprehensive unit tests for ConsistentHashRing

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Details

3cd4d75e50

Test all public methods with 100% coverage:
- AddNode: updates ring, is idempotent, handles multiple nodes
- RemoveNode: updates ring, handles non-existent nodes
- GetNode: returns consistent results, handles empty ring and single node
- GetNodes and IsEmpty helper methods

Distribution tests verify:
- Balanced key distribution across nodes (< 25% deviation)
- Minimal key movement when adding nodes (< 35% moved)
- Virtual nodes improve distribution (CV < 15%)
- Ring behavior with 100+ nodes

Includes benchmarks for GetNode, AddNode, and distribution operations.

Closes #2

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

HugoNijhuis commented

2026-01-09 15:53:53 +00:00

AI Code Review

This is an automated review generated by the code-reviewer agent.

Summary

Comprehensive test suite for ConsistentHashRing with excellent coverage of core functionality, edge cases, and performance characteristics. The tests verify consistent hashing properties, distribution balance, and minimal key movement. Well-structured and thorough implementation.

Findings

Code Quality

Excellent organization: Tests are logically grouped by functionality (constructor, AddNode, RemoveNode, GetNode, distribution, edge cases)
Clear test names: Function names follow TestX pattern and clearly indicate what is being tested
Good helper functions: minInt/maxInt helpers at lines 666-688 improve readability
TestConcurrentReadSafety (line 627): The comment correctly notes that the test verifies reads don't panic, but acknowledges mutex protection may be needed for true concurrent safety. This is honest and helpful.
Well-documented expectations: Tests like TestKeyDistribution_Balanced (line 271) clearly explain acceptable deviation thresholds with inline comments
TestDistributionStatistics (line 691): Uses t.Logf to output helpful diagnostics without failing tests unnecessarily

Potential Bugs

No obvious bugs found: Tests correctly handle edge cases and verify expected behavior
TestAddNode_Idempotent (line 57): Excellent test for idempotency - ensures adding the same node twice doesn't corrupt ring state
TestRemoveNode_NonExistent (line 132): Good defensive test ensuring removing non-existent nodes is a no-op
TestHash_DifferentKeys (line 476): Tests for hash collisions across 1000 keys, which is a realistic concern

Security Concerns

No security issues identified: The tests are for an internal data structure without external input or authentication concerns
The hash function uses SHA-256 (from hashring.go:89), which is cryptographically sound, though for this use case (distribution, not security) it's more than adequate

Style Notes

Consistent with Go conventions: Tests follow standard Go testing patterns
Good use of table-driven patterns: TestGetNode_Consistent (line 177) uses a slice of test keys
Line 666-688 helper functions: These are defined at the bottom but used earlier. Consider moving them above their first usage or to a separate test helpers file for better readability
Minor: TestHash_DifferentKeys (line 476): The keys variable (line 482) is created but never used after population except in error messages. This is fine but could be simplified to not store the keys array at all
Benchmark naming: Benchmark functions (BenchmarkGetNode, BenchmarkAddNode, BenchmarkDistribution) follow Go conventions

Test Coverage

Comprehensive coverage: Tests cover all public methods (NewConsistentHashRing, AddNode, RemoveNode, GetNode, GetNodes, IsEmpty)
Edge cases well-tested:
- Empty ring (TestGetNode_EmptyRing)
- Single node (TestGetNode_SingleNode)
- Many nodes - 100+ (TestRingBehavior_ManyNodes)
- Various node ID formats (TestNodeIDFormats)
- Empty string node ID (line 575)
Consistent hashing properties verified:
- Minimal key movement (TestMinimalKeyMovement - line 500)
- Virtual nodes improve distribution (TestVirtualNodes_ImproveDistribution - line 358)
- Wrap-around behavior (TestWrapAround - line 545)
Distribution testing is thorough: Multiple tests verify balanced distribution with reasonable statistical thresholds
Performance benchmarks included: Three benchmark functions cover common operations
One consideration: No explicit test for concurrent writes (AddNode/RemoveNode from multiple goroutines). The comment in TestConcurrentReadSafety acknowledges this limitation.

Verdict

LGTM

This is high-quality test code that thoroughly validates the ConsistentHashRing implementation. The tests are well-structured, cover all acceptance criteria from issue #2, verify important distributed systems properties (consistent hashing, minimal key movement, balanced distribution), and include helpful edge cases. The code is ready to merge.

## AI Code Review > This is an automated review generated by the code-reviewer agent. ### Summary Comprehensive test suite for ConsistentHashRing with excellent coverage of core functionality, edge cases, and performance characteristics. The tests verify consistent hashing properties, distribution balance, and minimal key movement. Well-structured and thorough implementation. ### Findings #### Code Quality - **Excellent organization**: Tests are logically grouped by functionality (constructor, AddNode, RemoveNode, GetNode, distribution, edge cases) - **Clear test names**: Function names follow TestX pattern and clearly indicate what is being tested - **Good helper functions**: minInt/maxInt helpers at lines 666-688 improve readability - **TestConcurrentReadSafety (line 627)**: The comment correctly notes that the test verifies reads don't panic, but acknowledges mutex protection may be needed for true concurrent safety. This is honest and helpful. - **Well-documented expectations**: Tests like TestKeyDistribution_Balanced (line 271) clearly explain acceptable deviation thresholds with inline comments - **TestDistributionStatistics (line 691)**: Uses t.Logf to output helpful diagnostics without failing tests unnecessarily #### Potential Bugs - **No obvious bugs found**: Tests correctly handle edge cases and verify expected behavior - **TestAddNode_Idempotent (line 57)**: Excellent test for idempotency - ensures adding the same node twice doesn't corrupt ring state - **TestRemoveNode_NonExistent (line 132)**: Good defensive test ensuring removing non-existent nodes is a no-op - **TestHash_DifferentKeys (line 476)**: Tests for hash collisions across 1000 keys, which is a realistic concern #### Security Concerns - **No security issues identified**: The tests are for an internal data structure without external input or authentication concerns - The hash function uses SHA-256 (from hashring.go:89), which is cryptographically sound, though for this use case (distribution, not security) it's more than adequate #### Style Notes - **Consistent with Go conventions**: Tests follow standard Go testing patterns - **Good use of table-driven patterns**: TestGetNode_Consistent (line 177) uses a slice of test keys - **Line 666-688 helper functions**: These are defined at the bottom but used earlier. Consider moving them above their first usage or to a separate test helpers file for better readability - **Minor: TestHash_DifferentKeys (line 476)**: The keys variable (line 482) is created but never used after population except in error messages. This is fine but could be simplified to not store the keys array at all - **Benchmark naming**: Benchmark functions (BenchmarkGetNode, BenchmarkAddNode, BenchmarkDistribution) follow Go conventions #### Test Coverage - **Comprehensive coverage**: Tests cover all public methods (NewConsistentHashRing, AddNode, RemoveNode, GetNode, GetNodes, IsEmpty) - **Edge cases well-tested**: - Empty ring (TestGetNode_EmptyRing) - Single node (TestGetNode_SingleNode) - Many nodes - 100+ (TestRingBehavior_ManyNodes) - Various node ID formats (TestNodeIDFormats) - Empty string node ID (line 575) - **Consistent hashing properties verified**: - Minimal key movement (TestMinimalKeyMovement - line 500) - Virtual nodes improve distribution (TestVirtualNodes_ImproveDistribution - line 358) - Wrap-around behavior (TestWrapAround - line 545) - **Distribution testing is thorough**: Multiple tests verify balanced distribution with reasonable statistical thresholds - **Performance benchmarks included**: Three benchmark functions cover common operations - **One consideration**: No explicit test for concurrent writes (AddNode/RemoveNode from multiple goroutines). The comment in TestConcurrentReadSafety acknowledges this limitation. ### Verdict **LGTM** This is high-quality test code that thoroughly validates the ConsistentHashRing implementation. The tests are well-structured, cover all acceptance criteria from issue #2, verify important distributed systems properties (consistent hashing, minimal key movement, balanced distribution), and include helpful edge cases. The code is ready to merge.

HugoNijhuis merged commit 3cd4d75e50 into main

2026-01-09 15:53:57 +00:00

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Reference: flowmade-one/aether#30